Loss profile analysis

ABSTRACT

Apparatuses and methods are disclosed for applying radio frequency (RF) energy to an object in an energy application zone. At least one processor may be configured to cause RF energy to be applied at a plurality of electromagnetic field patterns to the object in the energy application zone. The processor may be further configured to determine an amount of power dissipated in the energy application zone, for each of the plurality of field patterns. The processor may also be configured to determine a spatial distribution of energy absorption characteristics across at least a portion of the energy application zone based on the amounts of power dissipated when the plurality of field patterns are applied to the energy application zone.

The present application claims the benefit of priority to U.S.Provisional Patent Application No. 61/282,980, filed on May 3, 2010;U.S. Provisional Patent Application No. 61/282,981, filed on May 3,2010; U.S. Provisional Patent Application No. 61/282,983, filed on May3, 2010; U.S. Provisional Patent Application No. 61/282,984, filed onMay 3, 2010; U.S. Provisional Patent Application No. 61/282,985, filedon May 3, 2010; and U.S. Provisional Patent Application No. 61/282,986,filed on May 3, 2010. Each of these applications is fully incorporatedherein in its entirety.

TECHNICAL FIELD

The present application relates to apparatus and methods for applyingelectromagnetic energy to an object.

BACKGROUND

Electromagnetic waves are commonly used to apply energy to objects.Typically, such objects are located in a cavity configured to receiveelectromagnetic energy. However, because the electromagnetic fielddistribution may be dependent on the properties (e.g., size of theobject), location, and orientation of the object as well ascharacteristics of the source from which the energy is applied, it isoften difficult to apply electromagnetic energy in a controllablemanner. One example of an electromagnetic energy application device is amicrowave oven. In a microwave oven, microwaves are used to applyelectromagnetic energy from an energy source to the object through air.The electromagnetic energy is then absorbed by the object and convertedto thermal energy, causing the temperature of the object to rise. Amicrowave oven cannot differentiate one region from another in theheating space and deliver controlled amounts of energy to these regions.That is, a typical microwave oven is “blind” to the object being heatedand cannot tell either the location or the energy absorptioncharacteristics of the object.

SUMMARY

Some exemplary aspects of the present disclosure may be directed to anapparatus and a method for applying electromagnetic energy to an objectin an energy application zone. The apparatus may include at least oneprocessor configured to cause electromagnetic energy to be applied at aplurality of electromagnetic field patterns to the object in the energyapplication zone. The processor may be further configured to determinean amount of power dissipated in the energy application zone, for eachof the plurality of field patterns. The processor may also be configuredto determine a spatial distribution of energy absorption characteristicsacross at least a portion of the energy application zone based on theamounts of power dissipated when the plurality of field patterns areapplied to the energy application zone.

The processor may be further configured to calculate the distribution ofenergy absorption characteristics based on at least one of anelectromagnetic field intensity associated with each of the plurality offield patterns, and power dissipated in the energy application zone ateach of the plurality of field patterns.

As used herein, an object (e.g., a processor) is described to beconfigured to perform a task (e.g., calculate a distribution), if, atleast in some embodiments, the object performs this task in operation.Similarly, when a task (e.g., control a distribution of electromagneticenergy) is described to be in order to establish a target result (e.g.,in order to apply a plurality of electromagnetic field patterns to theobject) this means that, at least in some embodiments, the task iscarried out such that the target result is accomplished.

In some embodiments, the processor may be configured to recurringlydetermine a distribution of energy absorption characteristics. A timelapse between two determinations of distributions of energy absorptioncharacteristics, for example, the time lapse between two successivedeterminations, may be a function of a magnitude of a difference betweenthe distributions measured at two previous determinations. For example,the time lapse between the second and third determinations may be afunction of the magnitude of a difference between the distributionsmeasured at the first and second determinations. In some embodiments, amagnitude of a difference between two distributions may be determined asa function of the two distributions. Examples of such functions mayinclude a difference between the amounts of energy applied to a givenlocation in the two distributions, and an average of energy differencebetween the distributions across some region. Alternatively oradditionally, the time lapse between two successive determinations ofdistributions of energy absorption characteristics may be a function ofcharacteristics of the object.

Further, the processor may be configured to cause differing amounts ofenergy to be applied to differing portions of the energy applicationzone based on the distribution of energy absorption characteristics. Theprocessor may also be configured to cause controlled amounts of energyto be absorbed at differing locations in the object.

Some exemplary aspects of the present disclosure may be directed to anapparatus and a method for applying electromagnetic energy to an object.The apparatus may comprise a source of electromagnetic energy. Inaddition, the apparatus may comprise an energy application zone.Moreover, the apparatus may comprise at least one processor. Theprocessor may be configured to cause electromagnetic energy to beapplied in a plurality of electromagnetic field patterns to the objectin the energy application zone. The processor may also be configured todetermine an amount of power dissipated in the energy application zonefor each of the plurality of field patterns. In addition, the processormay be configured to determine a spatial distribution of energyabsorption characteristics across at least a portion of the object basedon the amounts of power dissipated when the plurality of field patternsare applied to the energy application zone.

Some exemplary aspects of the present disclosure may be directed to anapparatus and a method for applying electromagnetic energy in the radiofrequency range (RF energy) to an energy application zone via at leastone radiating element. The apparatus may comprise at least oneprocessor. The processor may be configured to control distribution of RFenergy such that at least two mutually different electromagnetic fieldpatterns are applied to the energy application zone. In addition, theprocessor may be configured to determine an amount of power dissipatedin the energy application zone for each of the electromagnetic fieldpatterns. Moreover, the processor may be configured to determine aspatial distribution of energy absorption characteristics across atleast a portion of the energy application zone based on the amounts ofpower determined for each of the field patterns.

The preceding summary is merely intended to provide the reader with avery brief flavor of a few aspects of the invention, and is not intendedto restrict in any way the scope of the claimed invention. In addition,it is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed. It is noted thatthe term exemplary is used herein in the sense of serving as an example,instance, or illustration.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate various embodiments and exemplaryaspects of the present invention and, together with the description,explain principles of the invention. In the drawings:

FIG. 1 is a schematic diagram of an apparatus for applyingelectromagnetic energy to an object, in accordance with some exemplaryembodiments of the present invention;

FIG. 2 illustrates a modal cavity satisfying a modal condition, inaccordance with some exemplary embodiments of the present invention;

FIGS. 3A and 3B illustrate exemplary field patterns in a modal cavityconsistent with some embodiments of the invention;

FIGS. 3C and 3D illustrate exemplary field patterns in a modal cavityconsistent with some embodiments of the invention;

FIG. 4 illustrates an exemplary modulation space consistent with someembodiments of the invention;

FIG. 5A is a schematic diagram of an apparatus configured to performfrequency modulation on electromagnetic waves supplied to an energyapplication zone, in accordance with some embodiments of the invention;

FIG. 5B is another schematic diagram of an apparatus configured toperform frequency modulation on electromagnetic waves supplied to theenergy application zone, in accordance with some embodiments of theinvention;

FIG. 6 is a schematic diagram of an apparatus configured to performphase modulation on electromagnetic waves supplied to an energyapplication zone, in accordance with some embodiments of the invention;

FIG. 7A is a schematic diagram of an apparatus configured to performamplitude modulation on electromagnetic waves supplied to an energyapplication zone, in accordance with some embodiments of the invention;

FIG. 7B is another schematic diagram of an apparatus configured toperform amplitude modulation on electromagnetic waves supplied to anenergy application zone, in accordance with some embodiments of theinvention;

FIGS. 8A-8C illustrate exemplary energy application zone discretizationstrategies in accordance with some embodiments of the invention;

FIG. 9 illustrates an exemplary loss profile in the form of an image,consistent with some embodiments of the invention;

FIGS. 10A and 10B illustrate exemplary loss profiles in the form of alook-up table consistent with some embodiments of the invention;

FIG. 11 is a flow chart of exemplary steps of applying electromagneticenergy to an energy application zone consistent with some embodiments ofthe invention;

FIGS. 12A-12C illustrate field intensity distributions of modes that maybe excited in an energy application zone;

FIGS. 13A and 13B show calculated values of normalized electric fieldmagnitude of two modes excitable at the same frequency in a cavity.

FIG. 14 is a simplified block diagram of a processor configured toconstruct a loss profile based on feedback from an energy applicationzone, according to some embodiments.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An exemplary aspect of some embodiments includes determining a lossprofile of an energy application zone. A loss profile may be anyrepresentation of the way in which a dielectric property changes fromone place to another in the energy application zone. The energyapplication zone may be any volume of space to which electromagneticenergy may be applied. An energy application zone may be empty, or mayinclude an object or a portion of an object. The object in the energyapplication zone may occupy the zone wholly or partially.

An example of a loss profile may be a graph or table showing thedielectric constant or any other absorption property and/or relatedparameters associated with given location within the energy applicationzone, e.g., as a function of the distance from a given point. Anotherexample of a loss profile is a three-dimensional map, in which volumeportions of the energy application zone having different energyabsorption properties appear in different colors. Any otherrepresentation of one or more of these or other dielectric/absorptionproperties as a function of location in the energy application zone maybe used as a loss profile. In addition, the term loss profile may referto approximations of a spatial distribution of one or more dielectricproperties. For example, the actual spatial distribution may becalculated, simulated, or measured at some limited accuracy, which, attimes, may be quite low, to obtain a loss profile.

In some embodiments, a loss profile may be determined by an electronicdigital processor. The processor may determine the loss profile byapplying certain rules (e.g., calculations) to data (or signalsindicative of data) collected by detectors that may be placed inside,around, and/or outside of the energy application zone. The loss profilemay be determined by running a computer program which uses such data asinput, and provides the loss profile as output. The data may include anyvalue indicative of the absorption of electromagnetic energy at a givenlocation. In some embodiments, the electromagnetic energy may besupplied to the energy application zone by exciting differentelectromagnetic field patterns in the zone, and the data may includedifferent values of energy absorbability detected when the differentfield patterns are excited. Exciting a field pattern in the energyapplication zone may be accomplished by applying to the energyapplication zone an electromagnetic wave having a certain frequency,phase, and/or other characteristics corresponding to the field pattern.As used herein, the term “excited” is interchangeable with “generated,”“created,” and “applied.”

For example, if the energy application zone consists of two regions, onethat absorbs energy and one that substantially does not absorb energy,then field patterns that coincide with only the first region will beabsorbed, while field patterns that coincide only with the second regionwill not be absorbed. Thus, the location of the two regions may bededuced from knowledge of which field patterns cause energy absorptionand which do not. In more complicated cases, similar considerations maybe applied by solving, for example, equation (1), as discussed below.

Reference will now be made in detail to exemplary embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. When appropriate, the same reference numbers are usedthroughout the drawings to refer to the same or like parts.

As illustrated in FIGS. 1, 5A, 5B, 6, 7A and 7B, embodiments of theinvention may include a source of electromagnetic energy (e.g.,including structures such as a power supply 12 and/or oscillators 22,26). The source may be regulated by a processor 30, such that energy maybe applied to an energy application zone. Structures such as powersupply 12 and oscillators 22, 26 may be used to apply electromagneticenergy via one or more radiating elements 18 to a load such as object 50located in the energy application zone, which in the figures isillustrated as cavity 20. Processor 30 may be configured to controldistribution of electromagnetic energy. For example, the processor maycontrol the source directly. Alternatively or additionally, processor 30may control a signal emanating from the source, or downstream from thesource.

Processor 30 may be configured to control spatial distribution ofelectromagnetic energy such that a plurality of electromagnetic fieldpatterns is applied to the object in the energy application zone. Asdiscussed later in greater detail, by altering one or more variableparameters that may affect a field pattern in the energy applicationzone (e.g., frequency, amplitude, etc., referred to herein as“modulation space elements” (MSEs)), it is possible to change a fieldpattern in the energy application zone, e.g., in cavity 20. Thus,sequential adjustment of such variables may cause associated sequentialchanges in the field patterns applied to the energy application zone 20.

Such changes in field patterns often affect absorption by the objectbecause, for instance, different field patterns may be absorbeddifferently in the object. For example, changing a field pattern havinghigh energy intensity at areas that coincide with the object to apattern having lower energy intensity at areas that coincide with theobject may reduce the amount of energy absorbed by the object. FIGS. 3Aand 3B, which each conceptually depict differing field patterns, areillustrative. In FIG. 3A the field pattern's high intensity areas 62(a/k/a “hot spots”) coincide with object 66. In contrast, with the fieldpattern of FIG. 3B there is no such coincidence with object 66.Therefore, object 66 is likely to absorb more energy when the fieldpattern of FIG. 3A is applied than when the field pattern of FIG. 3B isapplied.

As discussed later in greater detail, non-absorbed energy may bereflected or otherwise transmitted to radiating element 18 and detectedusing detector 40. By receiving signals from detector 40, for each fieldpattern applied, the processor may be able to calculate an amount ofpower dissipated in the energy application zone 20. And by aggregatingamounts of power dissipated by the energy application zone at variousfield patterns, processor 30 may then determine a spatial distributionof energy absorption characteristics across at least a portion of theobject.

The determined spatial distribution of energy absorption characteristic(which may also be referred to as a determined loss profile) may serveas an indicator of how the object may absorb energy as energyapplication continues. Thus, once an energy absorption characteristicprofile is known or estimated, the processor may be able to controlenergy application such that a desired energy absorption profile in theobject is achieved.

When feedback information related to energy absorption by object 50 iscombined with information about a plurality of known field patternscausing the feedback, processor 30 may be able to estimate the locationof object 50 in energy application zone 20. Therefore, over an iterativeseries of applied field patterns, processor 30 may be able to identifyareas where a load is present and areas where a load is absent. Byaggregating this information, the general location of the load may beascertained. And as the amount of applied field patterns and associatedfeedback increases, resolution may be increased. In some embodiments,the resolution may be increased to a point where a physical profile ofthe load (including, e.g., its contours) may be constructed.

In some respects, the invention may involve apparatus and methods forapplying electromagnetic energy to an object in an energy applicationzone. As used herein, the term “apparatus” in its broadest sense mayinclude any component or group of components described herein. Forexample, an “apparatus” as broadly used herein may refer only to aprocessor, such as processor 30, as illustrated, for example, in FIGS. 1and 5A, 5B, 6, 7A, and 7B. Alternatively or additionally, an “apparatus”may include a combination of a processor and one or more radiatingelements; a cavity, and one or more radiating elements; a source ofelectromagnetic energy; a processor, a cavity, one or more radiatingelements, and a source of electromagnetic energy; or any othercombination of components described herein.

The term electromagnetic energy, as used herein, includes any or allportions of the electromagnetic spectrum, including but not limited to,radio frequency (RF), infrared (IR), near infrared, visible light,ultraviolet, etc. In some cases, applied electromagnetic energy mayinclude RF energy with a wavelength of 100 km to 1 mm, which is afrequency of 3 KHz to 300 GHz, respectively. In some cases, RF energywithin a narrower frequency range, e.g., 1 MHz-100 GHz, may be applied.Microwave and ultra high frequency (UHF) energy, for example, are bothwithin the RF range. Even though examples of the invention are describedherein in connection with the application of RF energy, thesedescriptions are provided to illustrate a few exemplary principles ofthe invention, and are not intended to limit the invention to anyparticular portion of the electromagnetic spectrum. However, the methodsand apparatus described may be particularly useful for dealing withobjects that are smaller than a wavelength of the appliedelectromagnetic energy. Furthermore, the described methods and apparatusmay be particular useful when the energy application zone comprises amodal cavity, as defined below.

Similarly, this disclosure contains a number of examples ofelectromagnetic energy used for heating. Again, these descriptions areprovided to illustrate exemplary principles of the invention. Theinvention, as described and claimed, may provide benefit for variousproducts and industrial, commercial, and consumer processes involvingthe application of energy, regardless of whether the application ofenergy results in a temperature rise. For example, electromagneticenergy may be applied to an object for heating, combusting, thawing,defrosting, cooking, drying, accelerating reactions, expanding,evaporating, fusing, causing or altering biologic processes, medicaltreatments, preventing freezing or cooling, maintaining the objectwithin a desired temperature range, or any other application where it isdesirable to apply energy.

Moreover, reference to an “object” (also known as a “load”) to whichelectromagnetic energy is applied is not limited to a particular form.An “object” may include a liquid, solid, or gas, depending upon theparticular process with which the invention is utilized, and the objectmay include composites or mixtures of matter in one or more differingphases. Further, although the term “object” is in the singular, it mayrefer to multiple items or detached parts or components. Thus, by way ofnon-limiting example, the term “object” may encompass such matter asfood to be thawed or cooked; clothes or other material to be dried;frozen material (e.g., organs) to be thawed; chemicals to be reacted;fuel or other combustible material to be to be combusted; hydratedmaterial to be dehydrated; gases to be expanded; liquids to be thawed,heated, boiled or vaporized; blood or blood components (e.g., bloodplasma or red blood cells) to be thawed and/or warmed; materials to bemanufactured; components to be connected; or any other material forwhich there is a desire to apply, even nominally, electromagneticenergy.

In accordance with some embodiments of the invention, an apparatus ormethod may involve the use of an “energy application zone.” An energyapplication zone may be any void, location, region, or area whereelectromagnetic energy may be applied. It may include a hollow, and/ormay be filled or partially filled with liquids, solids, gases, orcombinations thereof. By way of example only, an energy application zonemay include the interior of an enclosure, interior of a partialenclosure (e.g., conveyor belt oven), interior of a conduit, open space,solid, or partial solid, which allows for the existence, propagation,and/or resonance of electromagnetic waves. The zone may be permanent ormay be temporarily constituted for purposes of energy application. Forease of discussion, all such alternative energy application zones mayalternatively be referred to as cavities, with the understanding thatthe term “cavity” implies no particular physical structure other than anarea in which electromagnetic energy may be applied.

The energy application zone may be located in an oven, chamber, tank,dryer, thawer, dehydrator, reactor, furnace, cabinet, engine, chemicalor biological processing apparatus, incinerator, material shaping orforming apparatus, conveyor, combustion zone, or any area where it maybe desirable to apply energy. Thus, consistent with some embodiments,the electromagnetic energy application zone may be an electromagneticresonator (also known as cavity resonator, resonant cavity, or simply“cavity”). The electromagnetic energy may be delivered to an object whenthe object or a portion thereof is located in the energy applicationzone.

An energy application zone may have a predetermined shape or a shapethat is otherwise determinable, so long as physical aspects of itsspatial form or contour are known at a time of energy application. Theenergy application zone may assume any shape that permitselectromagnetic wave propagations inside the energy application zone.For example, all or part of the energy application zone may have across-section that is spherical, hemispherical, rectangular, toroidal,circular, triangular, oval, pentagonal, hexagonal, octagonal,elliptical, or any other shape or combination of shapes. It is alsocontemplated that the energy application zone may be closed, e.g.,completely enclosed by conductor materials, bounded at least partially,or open, e.g., having non-bounded openings. The general methodology ofthe invention is not limited to any particular cavity shape,configuration, or degree of closure of the energy application zone,although in some applications, a high degree of closure or specificshapes may be preferred.

By way of example, an energy application zone, such as cavity 20, isillustrated diagrammatically in FIG. 1, where object 50 is positioned incavity 20. It is to be understood that object 50 need not be completelylocated in the energy application zone. That is, object 50 may beconsidered to be “in” the energy application zone if at least a portionof the object is located in the zone.

Consistent with some of the presently disclosed embodiments,electromagnetic waves of at least one wavelength may resonate in theenergy application zone. In other words, the energy application zone maysupport at least one resonant wavelength. For example, cavity 20 may bedesigned with dimensions permitting it to be resonant in a predeterminedrange of frequencies (e.g., the UHF or microwave range of frequencies,for example, between 300 MHz and 3 GHz, or between 400 MHz and 1 GHZ).Depending on the intended application, the dimensions of cavity 20 maybe designed to permit resonances in other ranges of frequencies in theelectromagnetic spectrum. The term “resonant” or “resonance” refers tothe tendency of electromagnetic waves to oscillate in the energyapplication zone at larger amplitudes at some frequencies (known as“resonance frequencies”) than at others. Electromagnetic wavesresonating at a particular resonance frequency may have a corresponding“resonance wavelength” that is inversely proportional to the resonancefrequency, determined via λ=c/f; where λ is the resonance wavelength, fis the resonance frequency, and c is the propagating speed of theelectromagnetic waves in the energy application zone. The propagatingspeed may change depending on the medium through which the wavepropagates. Therefore, when the energy application zone comprises morethan one material (for instance, load and void), c may not be uniquelydefined. Nevertheless, resonance wavelengths may be uniquely determinedusing a slightly different relation, including, for example, using anestimation based on c of the major component or an average of the c ofmiscellaneous components, or any other technique known in the art.

Among the resonant wavelengths that are supported by the energyapplication zone, there may be a largest resonant wavelength. Thelargest resonant wavelength may be determined uniquely by the geometryof the zone. In some embodiments, the largest resonant wavelength of anygiven energy application zone may be determined or estimated as known inthe art, for example, experimentally, mathematically and/or bysimulation. In some embodiments, the largest resonant wavelength may beknown in advance (e.g., retrieved from a memory or programmed into aprocessor). By way of example, FIG. 2 illustrates a rectangular cavity20 of dimensions length a, width b, and height c. Cavity 20 may supporta plurality of resonant wavelengths, the largest resonant wavelengthamong which is λ₀. If a>b>c, then the largest resonant wavelength λ0 isgiven by

$\frac{2{ab}}{\sqrt{a^{2} + b^{2}}}.$

By way of another example, if the energy application zone is a cubic ofdimensions a×a×a, then the largest resonant wavelength is given by√{square root over (2)}a. In yet another example, if the energyapplication zone is a cylinder (for example as illustrated in FIG. 2) ofradius a and length d, then the largest resonant wavelength is given by

$\frac{2\pi \; a}{2.405}$

if 2a>d, and

$\frac{2\pi \; a}{\sqrt{1.841^{2} + \left( \frac{\pi \; a}{d} \right)^{2}}}$

if 2a<d. In another example, if the energy application zone is a sphereof radius a, then the largest resonant wavelength is given by

$\frac{2\pi \; a}{2.744}.$

The forgoing examples are simply meant to illustrate that regardless ofshape, each energy application zone may have at least one resonantdimension.

Consistent with presently disclosed embodiments, an apparatus or methodmay involve the use of a source configured to deliver electromagneticenergy to the energy application zone. A “source” may include anycomponent(s) that are suitable for generating and supplyingelectromagnetic energy. Consistent with the presently disclosedembodiments, electromagnetic energy may be supplied to the energyapplication zone in the form of propagating electromagnetic waves (alsoknown as electromagnetic radiation) at predetermined wavelengths orfrequencies. As used herein, “propagating electromagnetic waves” mayinclude resonating waves, standing waves, evanescent waves, and wavesthat travel through a medium in any other manner. Electromagneticradiation carries energy that may be imparted to (or dissipated into)matter with which it interacts.

By way of example, and as illustrated in FIG. 1, the source may includeone or more of a power supply 12 configured to generate electromagneticwaves that carry electromagnetic energy. For example, power supply 12may be a magnetron configured to generate microwave waves at least onepredetermined wavelength or frequency. In some embodiments, themagnetron may be configured to generate high power microwaves.Alternatively or additionally, power supply 12 may include asemiconductor oscillator, such as a voltage controlled oscillator,configured to generate AC waveforms (e.g., AC voltage or current) with acontrollable frequency. AC waveforms may include sinusoidal waves,square waves, pulsed waves, triangular waves, and/or other types ofwaveforms with alternating polarities. Additionally or alternatively, asource of electromagnetic energy may include any other power supply,such as electromagnetic field generator, electromagnetic flux generator,or any mechanism for causing electrons to vibrate.

In some embodiments, the apparatus may include at least one modulator 14configured to modify one or more characteristic parameters of theelectromagnetic waves generated by power supply 12, in a controlledmanner. The modulator may or may not be part of the source. For example,modulator 14 may be configured to modify one or more parameters of aperiodic waveform, including amplitude (e.g., an amplitude differencebetween different radiating elements), phase, and frequency.

In some embodiments, modulator 14 may include at least one of a phasemodulator, a frequency modulator, and an amplitude modulator configuredto modify the phase, frequency, and amplitude of the AC waveform,respectively. These modulators are discussed in greater detail later, inconnection with FIGS. 5A, 5B, 6, and 7B. In some embodiments, modulator14 may be integrated as part of power supply 12 or the source, such thatthe AC waveforms generated by power supply 12 may have at least one of avarying frequency, a varying phase, and a varying amplitude over time.

The apparatus may also include an amplifier 16 for amplifying, forexample, the AC waveforms before or after they are modified by modulator14. The amplifier may or may not be part of the source. Amplifier 16 maybe, for example, a power amplifier including one or more powertransistors. As another example, amplifier 16 may be a step-uptransformer having more turns in the secondary winding than in theprimary winding. In other embodiments, amplifier 16 may also be a powerelectronic device such as an AC-to-DC-to-AC converter. Alternatively oradditionally, amplifier 16 may include any other device(s) or circuit(s)configured to scale up an input signal to a desired level.

The apparatus may also include at least one radiating element 18configured to transmit the electromagnetic energy to object 50.Radiating element 18 may include one or more waveguides and/or one ormore antennas (also known as power feeds) for supplying electromagneticenergy to object 50. For example, radiating element 18 may include slotantennas. Additionally or alternatively, radiating element 18 mayinclude waveguides or antennas of any other kind or form, or any othersuitable structure from which electromagnetic energy may be emitted.

Power supply 12, modulator 14, amplifier 16, and radiating element 18(or portions thereof) may be separate components or any combination ofthem may be integrated as a single component. Power supply 12, modulator14, amplifier 16, and radiating element 18 (or portions thereof) may beparts of the source. For example, a magnetron may be used as powersupply 12 to generate electromagnetic energy, and a waveguide may bephysically attached to the magnetron for transmitting the energy toobject 50. Alternatively or additionally, the radiating element may beseparate from the magnetron. Similarly, other types of electromagneticgenerators may be used where the radiating element may be for examplephysically separate from- or part of the generator or otherwiseconnected to the generator.

In some embodiments, more than one radiating element may be provided.The radiating elements may be located on one or more surfaces definingthe energy application zone. Alternatively, radiating elements may belocated inside and/or outside the energy application zone. When theradiating elements are located outside the zone, they may be coupled toelements that would allow the radiated energy to reach the energyapplication zone. Elements for allowing the radiated energy to reach theenergy application zone may include, for example, wave guides and/orantennas. The orientation and configuration of each radiating elementmay be distinct or the same, as may be required for obtaining a targetgoal, for example, application of a desired energy distribution in theenergy application zone. Furthermore, the location, orientation, and/orconfiguration of each radiating element may be predetermined beforeapplying energy to object 50, or dynamically adjusted using a processorwhile applying energy. The invention is not limited to radiatingelements having particular structures or which are necessarily locatedin particular areas or regions. In some embodiments, radiating elementsmay be placed in certain places, or the amplitudes of waves emitted fromdifferent radiating elements may be selected in accordance with thelocation, orientation, and/or configuration of the radiating elements.

One or more of radiating element(s) 18 may be configured to receiveelectromagnetic energy, optionally, in addition to radiatingelectromagnetic energy. In other words, as used herein, the term“radiating element” broadly refers to any structure from whichelectromagnetic energy may radiate and/or by which electromagneticenergy may be received, regardless of whether the structure wasoriginally designed for the purposes of radiating or receiving energy,and regardless of whether the structure serves any additional function.Thus, an apparatus or method consistent with presently disclosedembodiments may involve the use of one or more detectors configured todetect signals associated with electromagnetic waves received by the oneor more radiating elements. For example, as shown in FIG. 1, a detector40 may be coupled to radiating elements 18 that, when functioning asreceivers, receive electromagnetic waves from cavity 20.

As used herein, the term “detector” may include an electric circuit thatmeasures one or more parameters associated with electromagnetic waves.For example, such a detector may include a power meter configured todetect a level of the power associated with the incident, reflectedand/or transmitted electromagnetic wave (also known as “incident power,”“reflected power,” and “transmitted power”, respectively), an amplitudedetector configured to detect an amplitude of the wave, a phase detectorconfigured to detect a phase of the wave respective to a predefinedreference point, a phase difference between waves simultaneously emittedby two radiating elements, or other phase difference, a frequencydetector configured to detect a frequency of the wave, and/or any othercircuit suitable for detecting a characteristic of an electromagneticwave.

Incident power may be supplied from the source to a radiating elementfor emitting the power into the energy application zone 20. Of theincident power, a portion may be dissipated by the object (referred toherein as “dissipated power”). Another portion may be reflected at theradiating element (referred to herein as “reflected power”). Reflectedpower may include, for example, power reflected back to the radiatingelement via the object and/or the energy application zone. Reflectedpower may also include power retained by the port of the radiatingelement (e.g., power that is emitted by the antenna but does not flowinto the zone). The rest of the incident power, other than the reflectedpower and dissipated power, may be transmitted to one or more radiatingelement functioning as receivers (referred to herein as “transmittedpower”). Energy may also leak to other places, such as into the walls ofthe cavity, through the door, etc. For simplicity, these portions of theenergy are not discussed herein. In some embodiments, it may beestimated that these portions of the energy are substantially low andmay be negligible.

In some embodiments, the detector may be a directional coupler,configured to allow signals to flow from the amplifier to the radiatingelements when the radiating elements function as transmitters (e.g.,when the radiating elements radiate energy), and to allow signals toflow from the radiating elements to the amplifier when the radiatingelements function as receivers (e.g., when the radiating element receiveenergy). Additionally or alternatively, the directional coupler may befurther configured to measure the power of a flowing signal. In someembodiments, the detector may also include other types of circuits thatmeasure the voltage and/or current at the ports.

Consistent with some presently disclosed embodiments, the source may beconfigured to deliver electromagnetic energy at a predeterminedwavelength, denoted as λ₁, to the object in the energy application zone,wherein the predetermined wavelength is greater than about one quarterof the largest resonant wavelength supported by the energy applicationzone, denoted as λ₀. This relationship between the largest resonantwavelength and the wavelength of the delivered electromagnetic energy,which is expressed as λ₁≧λ₀/4, may be referred to as the “modalcondition”. In other embodiments, a different relationship between thewavelength of the applied electromagnetic energy supplied by the sourceand the largest resonant wavelength supported by the energy applicationzone may be applied in order to meet the modal condition. In someembodiments, the modal condition is met when low order modes areexcited, e.g., m*n is below 30, 40, or 50 (wherein m and n are integersrepresenting the mode number in different axes, e.g., x and y). Thesource is not necessarily limited to configurations that supplieselectromagnetic energy at a single predetermined wavelength. Optionally,the source may be configured to supply electromagnetic energy to cavity20 at a set of wavelengths, which may be determined before energyapplication begins. When the source supplies energy to the cavity atvarying frequencies, the largest wavelength among which may be denotedλ₁, and the modal condition may be characterized as λ₁≧λ₀/4. In someembodiments, λ₁ may also have an upper limit, for example, it may besmaller or equal λ0.

Alternatively, the modal condition may be expressed in terms offrequency. Because there is a relationship between wavelengths λ₁ and λ₀and their corresponding frequencies f₁ and f₀, such that f₁=c/λ₁ andf₀=c/λ₀, the modal condition, λ₁≧λ₀/4, may be expressed as f₁≦4f₀, thatis, to operate within the modal condition, the electromagnetic energymay be applied at a frequency that is lower than about four times thelowest resonance frequency in the energy application zone.

In addition, because the largest resonant wavelength λ₀ has a uniquerelationship with the dimensions of the energy application zone, themodal condition may also be expressed as a relationship between thedimension(s) of the energy application zone and the applied wavelengthλ₁. For example, for a rectangular cavity 20 having length, width, andheight, a, b, and c respectively, and wherein a>b>c, the modal conditionmay be expressed as

$\lambda_{1} \geq \frac{ab}{2\sqrt{a^{2} + b^{2}}}$

As another example, for a cubic cavity having dimensions a×a×a, themodal condition may be expressed as

$\lambda_{1} \geq {\frac{\sqrt{2}a}{4}.}$

As another example, for spherical cavity having radius a, the modalcondition may be expressed as

$\lambda_{1} \geq {\frac{\pi \; a}{3.733}.}$

A cavity whose dimensions satisfy the “modal condition” in respect ofelectromagnetic energy supplied to the cavity, is referred to herein asa “modal cavity.”

By its nature, an electromagnetic field tends to be distributed in anuneven field pattern in the energy application zone. That is, a spatialdistribution of electric field intensity in the energy application zonemay be uneven. A field pattern may be substantially stable in space overtime, or spatially varying over time. The manner by which the fieldpattern varies over time may be known. A field pattern may result inareas with relatively high amplitude of electrical field intensity(corresponding to maxima or minima in the field amplitude) which arereferred to herein as “hot spots.” Examples of hot spots are illustratedby the shaded regions in FIGS. 3A-3D. A field pattern may also result inareas with relatively low amplitude of electrical field intensity (e.g.zero or near zero field values), referred to herein as “cold spots.”Examples of cold spots are illustrated by the non-shaded areas in FIGS.3A-3D. It is hereby noted that while hot spots are diagrammaticallyillustrated in the figures as having a clear and defined border, inreality the intensity changes in a more gradual manner between hot spotsand cold spots. In fact, energy transfer to the object may occur in allregions of the object that coincide with regions of the field pattern,where the field pattern has non-zero field intensity and is notnecessarily limited to areas coinciding with hot spots, The extent ofheating the object may depend, among other things, on the intensity ofthe field to which the object is exposed and the duration of exposure.

The field pattern itself may be a function of many factors (as discussedlater), including for example the physical characteristics anddimensions of the energy application zone. The relatively high amplitudeof electrical field intensity in a hot spot may be higher than a firstthreshold and the relatively low amplitude of electrical field intensityin a cold spot may be lower than a second threshold. The first thresholdmay be the same or different from the second threshold. In FIGS. 3A-3B,the first and second thresholds are the same. In some embodiments, thethresholds may be predetermined such that field intensity lower than oneof the thresholds may not effectively apply energy to the object. Forexample, the second threshold may be selected as being close to theminimum value of the field intensity. As used herein, the term“amplitude” is interchangeable with “magnitude.”

In the energy application zone, a particular region may be covered bythe relatively high amplitude of electrical field intensity (hot spots)of some field patterns, and relatively low amplitude of electrical fieldintensity (cold spots) of some other field patterns. Field patterns maybe selectively chosen to target energy delivery to selected regions ofthe energy applications zone. For example, if energy needs to be appliedto a first region but not a second region in the energy applicationzone, one or more field patterns may be selected in which hot spots ofthese filed patterns substantially coincide with the first region andcold spots substantially coincide with the second region. Therefore,consistent with some presently disclosed embodiments, the source may beconfigured to deliver electromagnetic energy in one or more fieldpatterns having hot and cold spots in predetermined areas of the energyapplication zone. In some embodiments, the controller may regulate thesource to apply energy using such field patterns to achieve a targetenergy distribution. In modal cavity 60, as illustrated in FIGS. 3A and3B, field patterns may be excited such that each has a plurality ofareas with high amplitudes of intensity (hot spots) 62 and 64 (shadedareas) and areas with low amplitudes of intensity (cold spots;non-shaded areas).

Some of the field patterns excitable in an energy application zone arenamed “modes”. Modes form a set of special field patterns that arelinearly independent from each other and orthogonal to one another. Asreferred herein, two field patterns are orthogonal to each other if theintegral of the scalar product of the two fields associated with the twomodes over the energy application zone is zero. A mode or a combinationof modes (e.g., a general field pattern), can be of any known type,including propagating, evanescent, and resonant. In some embodiments,the excited field pattern includes a combination of modes.

In FIGS. 3A and 3B, objects 66 and 68 are placed in energy applicationzone 60. If one desires to apply energy only to object 66 and to avoidapplying energy to object 68, the field pattern of FIG. 3A may bechosen. Alternatively, if there is a desire to apply energy to object 68and to avoid applying energy to object 66, the field pattern of FIG. 3Bmay be chosen.

Any field pattern that may be excited in an energy application zone andmay be represented mathematically as a linear combination of modes. Themodes may include an infinite number of evanescent modes and a finitenumber of propagating modes (some of which may be resonant modes). Ingeneral, fewer propagating modes may be excited in a modal cavity thanin a non-modal cavity. In other words, a modal cavity may support, ingeneral, fewer propagating modes than a non-modal cavity. Again, some ofthe supported propagating modes may be resonant modes. By nature, theevanescent modes have a very small percent of power (or energy) out ofthe total power (or energy) used to excite the field pattern, and thevast majority of the total power (and energy) is carried by propagatingmodes.

As explained in more detail below, in some embodiments, one or moreradiating elements may be placed such that some undesired modes may berejected. For example, two or more propagating modes may be effectivelyexcited in an energy application zone by a single frequency. If theradiating element emitting an electromagnetic wave at that frequency ispositioned at a null of one of the modes (i.e. at a location wherein oneof the modes has zero field), this mode may be eliminated (i.e.,rejected).

The modal condition and the corresponding modal cavity (i.e. a cavitywhich meets the modal condition) may exhibit advantages in controllingfield patterns, or more specifically, modes, in the energy applicationzone. As discussed above, in a modal cavity, the number of propagatingmodes may be fewer than that in a non-modal cavity. Therefore, controlof these propagating modes may be relatively easier, as the number anddensity of antennas used to eliminate undesired modes may be lower ifthe modal condition is met. Moreover, minor inaccuracies in control mayhave a less prominent overall effect on the hot spot selection in amodal cavity than in a non-modal cavity, where a relatively highernumber of modes may require finer control in order to achieve acondition in which one propagating mode is excited and others are not.

In one respect, an aspect of the invention may involve employing acertain combination of variable parameters (referred to herein as MSE)that may affect the field pattern excited in the energy applicationzone, in order to purposefully achieve cold spots (e.g., areas havingrelatively low amplitude of electrical field intensity) in specifiedareas in the energy application zone. These areas then permit controlledapplication of energy because when it is desired to avoid applyingenergy to a portion of an object, that portion may be aligned with acold spot. Alternatively, the device may be operated such that anelectromagnetic field is excited that has a hot spot (e.g., relativelyhigh amplitude of electrical field intensity) aligned with a portion ofan object where it is desired to apply energy. For example, by choosingto excite the field pattern as shown in FIG. 3A, one may heat object 66and avoid heating object 68, while by choosing to excite the fieldpattern as shown in FIG. 3B one may heat object 68 and avoid heatingobject 66. Thus, when it is desired to apply energy to a portion of anobject in an energy application zone, a higher intensity area of a fieldpattern may be aligned with that portion of the object. While the modalcondition may be used in combination with MSE control, the modalcondition may also provide benefits even if not used with MSE control,and conversely, MSE control may be applied even if the modal conditionis not met.

If a user desires to apply twice the amount of energy to object 66 thanto object 68, the field patterns of both FIG. 3A and FIG. 3B may beused, with the former being applied for double the amount of time at thesame power level, at double the power level for the same amount of time,or for any other time/power pair that corresponds supplying twice theenergy via the field pattern of FIG. 3A than via the field pattern ofFIG. 3B (assuming that the fields have similar intensities in the shadedareas). If the field intensities differ in the shaded areas, thedifference may be taken into account in order to achieve a desiredenergy application profile in the energy application zone or the object,e.g., a desired energy absorption distribution in the energy applicationzone or the object.

When two field patterns are excited sequentially, the time average ofthe field patterns formed in the energy application zone may berepresented as the sum of the two excited field patterns. If the fieldpatterns are excited simultaneously, interference may occur, and thetime average may be different from the sum. However, if the two fieldpatterns are orthogonal to each other (e.g., modes), sequential andsimultaneous application may each have the same result.

In order to control the amounts of energy that are applied to twodifferent regions, it may be desirable to first determine the energyabsorption characteristics of the two regions. Differing regions in theenergy application zone may have differing energy absorptioncharacteristics. For example in a situation where bread and vegetablesare heated by RF energy, a region consisting mostly of bread may be lessabsorptive than another region consisting mostly of vegetables. Inanother example, a bread portion that coincides only with a fieldpattern characterized by a first frequency may have different energyabsorption characteristics than a second bread portion, which coincidesonly with a field pattern, characterized by a second frequency,different from the first.

In some embodiments, an apparatus or method of the invention may involveone or more processors configured to determine the energy absorptioncharacteristics of any given object placed at least partially in theenergy application zone. Determination of the energy absorptioncharacteristics may be accomplished through feedback (e.g., viareflection, as discussed later in greater detail). Alternatively, insituations where absorptive characteristics of object(s) in the energyapplication zone are already known, an apparatus consistent withpresently disclosed embodiments need not determine energy absorptivecharacteristics. Rather, related information may be preprogrammed orotherwise provided to the processor, for example, using machine readabletags.

As used herein, the term “processor” may include an electric circuitthat executes one or more instructions. For example, such a processormay include one or more integrated circuits, microchips,microcontrollers, microprocessors, all or part of a central processingunit (CPU), graphics processing unit (GPU), digital signal processors(DSP), field-programmable gate array (FPGA) or other circuit suitablefor executing instructions or performing logic operations.

The instructions executed by the processor may, for example, bepre-loaded into the processor or may be stored in a separate memory unitsuch as a RAM, a ROM, a hard disk, a optical disk, a magnetic medium, aflash memory, other permanent, fixed, or volatile memory, or any othermechanism capable of providing instructions to the processor. Theprocessor(s) may be customized for a particular use, or can beconfigured for general-purpose use and perform different functions byexecuting different software.

If more than one processor is employed, all may be of similarconstruction, or they may be of differing constructions electricallyconnected or disconnected from each other. They may be separate circuitsor integrated in a single circuit. When more than one processor is used,they may be configured to operate independently or collaboratively. Theymay be coupled electrically, magnetically, optically, acoustically,mechanically or by other means permitting them to interact.

A single or multiple processors may be provided for the sole purpose ofdetermining a distribution of energy absorption characteristics acrossthe energy application zone. Alternatively, a single or multipleprocessors may be provided with the function of determining the energyabsorption characteristics in addition to providing other functions. Forexample, the same processor(s) may also be used to regulate the sourceor be integrated into a control circuit that provides additional controlfunctions to components other than the source.

Consistent with presently disclosed embodiments, the at least oneprocessor may be configured to apply a plurality of electromagneticfield patterns to the object in the energy application zone. The term“field pattern” may refer to a spatial distribution of electrical fieldintensity in the energy application zone. A field pattern may besubstantially stable in space over time, or spatially varying over time.The manner in which the field pattern varies over time may be known. Thepattern in which the energy is distributed may be a function of thephysical characteristics of the energy application zone; controllableaspects of the energy source; the type, configuration, orientation,and/or placement of the radiating elements; the presence of fieldaltering structures (e.g., field adjusting elements and/or dielectriclenses); and any other variable that may affect the field pattern. Afield adjusting element may be any element that may be controlled toaffect the field excited in the energy application zone (e.g., in a waythat selectively directs the electromagnetic energy from one or more ofradiating elements into the object).

By regulating source-related variables, including one or more offrequency, phase, relative amplitude, antenna selection, and/or antennaorientation, the processor may be able to cause a plurality of differingfield patterns to be applied to the energy application zone and/or anobject within the zone. Similarly, the processor may be able to cause aplurality of differing field patterns by other variables such as throughthe adjustment of FAEs (field adjusting elements); adjusting dielectriclenses; or by other means. All such controllablevariables/parameters/methods, and/or the combination of them, which mayachieve a predetermined set of field patterns in the energy applicationzone, are referred to herein as a “modulation space” or “MS”.

The term “modulation space” or “MS” is used to collectively refer to allthe parameters that may affect a field pattern in the energy applicationzone and all combinations thereof. In some embodiments, the “MS” mayinclude all possible components that may be used and their potentialsettings (either absolute or relative to others) and adjustableparameters associated with the components. For example, the “MS” mayinclude a plurality of variable parameters, the number of antennas,their positioning and/or orientation (if modifiable), the useablebandwidth, a set of all useable frequencies and any combinationsthereof, power settings, phases, etc. The MS may have any number ofpossible variable parameters, ranging between one parameter only (e.g.,a one dimensional MS limited to frequency only or phase only—or othersingle parameter), two or more dimensions (e.g., varying frequency andamplitude together within the same MS), or many more.

Examples of energy application zone-related factors that may affect themodulation space include the dimensions and shape of the energyapplication zone and the materials from which the energy applicationzone is constructed. Examples of energy source-related factors that mayaffect the modulation space include amplitude, frequency, and phase ofenergy delivery. Examples of radiating element-related factors that mayaffect the modulation space include the type, number, size, shape,configuration, orientation and placement of the radiating elements.

Each variable parameter associated with the MS may be thought of as anMS dimension. By way of example, FIG. 4 illustrates a three dimensionalmodulation space 400, with the three dimensions designated as frequency(F), phase (φ), and amplitude (A). That is, in MS 400, frequency, phase,and amplitude of the electromagnetic waves may be modulated duringenergy application, while all the other parameters may be predeterminedand fixed during energy application. An MS may also be one dimensionalwhere only one parameter is varied during the energy application, or maycontain many dimensions that are varied. In FIG. 4, the modulation spaceis depicted in three dimensions for ease of discussion only. The MS mayhave many more dimensions.

The term “modulation space element” or “MSE” may refer to a specific setof values of the variable parameters in MS. For example, FIG. 4illustrates an MSE 401 in the three-dimensional MS 400. MSE 401 has aspecific frequency F(i), a specific phase φ (i), and a specificamplitude A(i). If even one of these MSE variables change, then the newset defines another MSE. For example, (3 GHz, 30°, 12 V) and (3 GHz,60°, 12 V) represent two different MSEs, because the phase componentchanges. Thus, if an MSE can be visualized as a point in the modulationspace, then the aggregate of all MSEs define the modulation space.Differing combinations of these MS elements may lead to differing fieldpatterns across the energy application zone and differing energydistribution patterns in the object. For example, two MSEs may differone from another in the relative amplitudes of the energy being suppliedto a plurality of radiating elements, and these differences may resultin differing field patterns. A plurality of MSEs may be executedsequentially or simultaneously to excite a particular field pattern inthe energy application zone.

The sequential (and/or simultaneous) choice of MSEs may be referred toas an “energy delivery scheme.” For example, an energy delivery schememay consist of three MSEs (F(1), φ(1), A(1)), (F(2), φ(2), A(2)), (F(3),φ(3), A(3)). Since there are a virtually infinite number of MSEs, thereare a virtually infinite number of different energy delivery schemes,resulting in virtually infinite number of differing field patterns inany given energy application zone (although different MSEs may at timescause highly similar or even identical field patterns). Of course, thenumber of differing energy delivery schemes may be, in part, a functionof the number of MSEs that are available. The invention is not limitedto any particular number of MSEs or MSE combinations. Rather, the numberof options that may be employed could be as few as two or as many as thedesigner desires, depending on factors such as intended use, level ofdesired control, hardware or software resolution and cost. For example,exciting a larger number of differing field patterns, which may allow amore subtle design of a field pattern in the energy application zone,may require a larger number of MSEs. In such cases, at least 3 MSEs maybe required, for example, 3, 4, or 5 MSEs. In some embodiments, thenumber of MSEs is very large, but only few of them are used forexcitation. For example, 400 different frequencies may be available, andin a given energy application cycle only 5 of them may be used. Thesefive frequencies may be, for example, MSEs that cause the excitation ofdifferent resonating modes in the energy application zone.

With the possible MSE selections, the processor may determine a set ofsuitable MSEs depending on particular application. For example, apredetermined set of field patterns may be selectively chosen andapplied to the energy application zone using selected MSEs, such that aparticular region may be covered by high field intensity areas of onefield pattern but by low field intensity areas of another. For example,object 66 is covered by the high field intensity areas of the fieldpattern of FIG. 3A but by the low field intensity areas of the fieldpattern of FIG. 3B. Therefore, when energy absorbed in connection withthe field pattern of FIG. 3A is measured, the measurement may beindicative of energy absorption characteristics of object 66. Likewise,a measurement of energy absorbed in connection with the field pattern ofFIG. 3B may be indicative of energy absorption characteristics of object68.

The apparatus of FIG. 1 may be configured to regulate the source to forma set of different MSEs and apply their corresponding field patterns tothe energy application zone. Consistent with some embodiments, suchregulation may occur through the selection and control of “MSEs”. Sincea particular field pattern corresponds to one or more controllablevariables (e.g., MSEs), the processor may be configured to alter MSEs inorder to achieve differing field patterns in the energy applicationzone.

For example, as depicted in FIG. 1, an exemplary processor 30 may beelectrically coupled to various components of the source, such as powersupply 12, modulator 14, amplifier 16, and radiating elements 18.Processor 30 may be configured to execute instructions that regulate oneor more of these components. For example, processor 30 may regulate thelevel of power supplied by power supply 12. Alternatively oradditionally, processor 30 may regulate the amplification ratio ofamplifier 16, by switching the transistors in the amplifier.Alternatively or additionally, processor 30 may performpulse-width-modulation control of amplifier 16 such that the amplifieroutputs a desired waveform. Processor 30 may regulate modulationsperformed by modulator 14. In another example, processor 30 mayalternatively or additionally regulate at least one of location,orientation, and configuration of each radiating element 18, such asthrough an electro-mechanical device. Such an electromechanical devicemay include a motor or other movable structure for rotating, pivoting,shifting, sliding or otherwise changing the orientation or location ofone or more radiating elements 18. Processor 30 may be further configureto regulate any field adjusting elements located in the energyapplication zone, in order to change the field pattern in the zone. Forexample, field adjusting elements may be configured to selectivelydirect the electromagnetic energy from the radiating element, or tosimultaneously match the radiating element that acts as a transmitter toreduce coupling to the other radiating elements that act as receivers.Alternatively or additionally, processor 30 may selectively distributeenergy between radiating elements and/or may selectively use only asubset of available radiating elements.

The processor may regulate one or more components of the source andparameters associated with the components, according to a predeterminedscheme. For example, when a phase modulator is used, it may becontrolled to perform a predetermined sequence of time delays on an ACwaveform emitted by a radiating element, such that the phase of the ACwaveform is increased by a number of degrees (e.g., 10 degrees) for eachof a series of time periods. Alternatively or additionally, theprocessor may dynamically and/or adaptively regulate modulation based onfeedback from the energy application zone. For example, processor 30 maybe configured to receive an analog or digital feedback signal fromdetector 40, indicating an amount of electromagnetic energy receivedfrom cavity 20, and processor 30 may dynamically determine a time delayat the phase modulator for the next time period based on the receivedfeedback signal.

The processor may also be configured to regulate a frequency modulatorin order to alter a frequency of at least one electromagnetic wavesupplied to the energy application zone. Such a frequency modulator maybe configured to adjust the frequency of an AC waveform. By way ofexample, the frequency modulator may be a semiconductor oscillator, suchas oscillator 22 diagrammatically depicted in FIG. 5A, and configured togenerate an AC waveform oscillating at a predetermined frequency. Thepredetermined frequency may be in association with an input voltage,current, or other analog or digital signals. For example, a voltagecontrolled oscillator may be configured to generate waveforms atfrequencies proportional to the input voltage.

Consistent with some embodiments, processor 30 may be configured toregulate oscillator 22 to generate AC waveforms of time-varyingfrequencies. The AC signal may be amplified by amplifier 24 and causeantennas 32 and 34 to excite frequency modulated electromagnetic wavesin cavity 20.

Processor 30 may be configured to regulate oscillator 22 to sequentiallygenerate AC waveforms oscillating at various frequencies within apredetermined frequency band. This sequential process may be referred toas “frequency sweeping.” More generally, processor 30 may be configuredto regulate the source to sequentially generate waveforms at variousMSEs, e.g. at various frequencies, phases, amplitudes, and/or selectionsof radiating elements. Such a sequential process may be referred as “MSEsweeping”. Sequentially swept MSEs may not necessarily be related toeach other. Rather, their MSE variables may differ significantly fromMSE to MSE (or may be logically related). In some embodiments, the MSEvariables may differ significantly from MSE to MSE, possibly with littleor no logical relation among them, however in the aggregate, a group ofworking MSEs may achieve a desired energy application goal.

In frequency sweeping, each frequency may be associated with a feedingscheme (e.g., a particular MSE, being a particular combination ofelements and their settings). In some embodiments, based on the feedbacksignal provided by detector 40, processor 30 may be configured to selectone or more frequencies from the frequency band, and regulatesoscillator 22 to sequentially generate AC waveforms at these selectedfrequencies.

Alternatively or additionally, processor 30 may be configured toregulate amplifier 24 to adjust amounts of energy delivered via antennas32 and 34, based on the feedback signal. Consistent with someembodiments, detector 40 may detect an amount of energy reflected fromthe energy application zone at a particular frequency, and processor 30may be configured to cause the amount of energy applied at thatfrequency to be high when the reflected energy is high. That is,processor 30 may be configured to cause one or more antennas to applyenergy at a particular frequency over a longer duration when thereflected energy is high at that frequency. Alternatively, processor 30may be configured to cause one or more antennas to apply energy at aparticular frequency over a longer duration when the reflected energy islow at that frequency. For example, when the reflected energy measuredindicates that an object is present with relatively low absorptioncharacteristics (e.g., ice) it may be desirable to apply more energy atthat frequency. Other relationships between amounts of reflected andapplied energy may also be used.

As depicted in FIG. 5B, some embodiments of the invention may includemore than one oscillator, such as oscillators 22 and 26 for generatingAC waveforms of differing frequencies. The separately generated ACwaveforms may be amplified by amplifiers 24 and 28, respectively.Accordingly, at any given time, antennas 32 and 34 may be caused tosimultaneously apply electromagnetic waves at two differing frequenciesto cavity 20. Each of these two frequencies may be time-varying. FIG. 5Billustrates two oscillators for exemplary purposes only, and it iscontemplated that more than two oscillators (and/or more than twoamplifiers and/or more than two antennas) may be used.

The processor may be configured to regulate a phase modulator in orderto alter a phase difference between two electromagnetic waves suppliedto the energy application zone. By way of example, the phase modulatormay include a phase shifter, such as phase shifter 54, illustrated inFIG. 6. Phase shifter 54 may be configured to cause a time delay in theAC waveform in a controllable manner within cavity 20, delaying thephase of an AC waveform anywhere from between 0-360 degrees. Phaseshifter 54 may include an analog phase shifter configured to provide acontinuously variable phase shift or time delay, or phase shifter 54 mayinclude a digital phase shifter configured to provide a discrete set ofphase shifts or time delays.

Consistent with some embodiments such as is illustrated in FIG. 6, asplitter 52 may be provided to split the AC signal generated byoscillator 22 into two AC signals (e.g., split signals). Processor 30may be configured to regulate phase shifter 54 to sequentially causevarious time delays such that the phase difference between the two splitsignals may vary over time. This sequential process may be referred toas “phase sweeping.”

The processor may be configured to regulate an amplitude modulator inorder to alter an amplitude of at least one electromagnetic wavesupplied to the energy application zone. By way of example, theamplitude modulator may include a mixer circuit, such as mixer 42illustrated in FIG. 7A, configured to regulate an amplitude of a carrierwave with another modulating signal. The modulated signal (e.g., theoutput of mixer 42) may be amplified by amplifiers 44.

Consistent with some embodiments, the amplitude modulator may includeone or more phase shifters, such as phase shifters 54 and 56, as shownin FIG. 7B. Amplitude modulation may be implemented by combining two ormore phase shifted electromagnetic waves. For example, splitter 52 maysplit the AC signal generated by oscillator 22 into two AC signals, suchas sinusoidal waves cos [φt]. Because they are split from a singlesignal, the two split AC signals may share substantially the samefrequency. One split AC signal may be shifted by phase shifter 54 forphase a, so that the AC signal becomes cos [φt+α]. The other split ACsignal may be shifted by phase shifter 56 for phase −α (or equivalently360°−α), so that the AC signal becomes cos [φt−α].

As illustrated in FIG. 7B, the phased shifted AC signals may beamplified by amplifier 24 and 28 respectively, and in this manner,antennas 32 and 34 may be caused to excite electromagnetic waves havinga shared AC waveform. Antennas 32 and 34 may be positioned atpredetermined positions, so that the two electromagnetic waves excitedby the antennas may be combined to form an amplitude modulated wave,according to the trigonometric identity cos [φpt−α]+cos [φt+α]=2 cos(α)cos(φt).

Although for ease of discussion FIGS. 5A-5B, FIG. 6 and FIG. 7A-7Billustrate circuits for altering frequency, phase, and amplitudemodulations individually it is contemplated that components of thesecircuits may be combined in order to enable multiple combinations,thereby providing a larger modulation space. Moreover, many radiatingelements may be employed, and differing wave patterns may be achievedthrough the selective use of radiating elements. By way of example only,in an apparatus having three radiating elements A, B, and C, amplitudemodulation may be performed with radiating elements A and B, phasemodulation may be performed with radiating elements B and C, andfrequency modulation may be performed with radiating elements A and C.Optionally, any modulation may be performed with any combinations ofradiating elements (e.g., each having a different phase, and/or adifferent amplitude and/or a different frequency). Alternatively,amplitude may be held constant and field changes may be caused byswitching between radiating elements. Further, radiating elements 32 and34 may include a device that causes their location or orientation tochange, thereby causing field pattern changes. The combinations arevirtually limitless, and the invention is not limited to any particularcombination, but rather reflects the notion that field patterns may bealtered by altering one or more of the parameters in the modulationspace (MS), thereby varying MSEs

As previously discussed, the processor may play a role in causing aplurality of electromagnetic field patterns to be applied to an objectthrough regulation of variables that alter MSEs, and hence alter thefield pattern applied. For example, the field patterns may be predictedbased on the MSEs selected. This prediction may be possible as theresult of testing, simulation, and/or analytical calculation. Theresulting predictability permits a set of MSEs to be chosen in order toachieve a desired energy application profile.

Using the testing approach, sensors (e.g., small antenna) may be placedin an energy application zone, to measure the field distribution thatresults from a given MSE. The distribution can then be stored in, forexample, a look-up table.

In a simulated approach, a virtual model may be constructed so that MSEscan be tested in a virtual manner. For example, a simulation model of anenergy application zone may be performed in a computer based on a set ofMSEs inputted to the computer. A simulation engine such as CST or HFSSmay be used to numerically calculate the field distribution inside theenergy application zone. The correlation between MSE and resulting fieldpattern may be established in this manner. This simulated approach canoccur well in advance and the known combinations stored in a look-uptable, or the simulation can be conducted on an as-needed basis duringan energy application operation, or associated with an energyapplication operation.

Similarly, as an alternative to testing and simulation, calculations maybe performed based on an analytical model in order to predict fieldpatterns based on selected combination of MSEs. For example, given theshape of an energy application zone with known dimensions, the at leastone processor may be configured to calculate some basic field patternscorresponding to given MSEs from analytical equations. These basic fieldpatterns, (e.g., “modes” or combination of modes) may then be used toconstruct an energy delivery scheme, as defined earlier. As with thesimulated approach, the analytical approach may occur well in advanceand the known combinations stored in a look-up table, or may beconducted on an as-needed basis during or shortly before an energyapplication operation.

Consistent with some embodiments, the calculation of field patterns maybe made without considering the existence of the object. This may bebased on the assumption that the existence of object in the energyapplication zone does not materially change the intensity distributionof the field pattern in the zone (known as the “Born approximation”).The Born approximation may be particularly useful when the location,size and electromagnetic characteristics of the object are unknownbefore the energy application. When the properties of the object areknown before hand, the field pattern calculation may also be made withconsideration of the object. Field calculation or simulation may berelatively simple in cases where the load fills the entire energyapplication zone and is dielectrically homogeneous.

A load maybe considered to fill substantially the entire energyapplication zone if the load fills at least 90% of the zone. In someembodiments, the load may fill the entire zone except for some excludedspace, for example, space containing radiating elements (e.g., RFfeeds), detectors, thermometers, or other equipment that may be usefulfor the operation of the apparatus. Some marginal spaces that are notfilled by the object, for example, at corners of a cavity, may alsoexist in a substantially filled energy application zone.

An example of a homogeneous load is one with no dielectric-boundaries. Adielectric boundary is a line or surface that separates between tworegions, each having a significantly different dielectric constant(∈_(r)). A characteristic size of each of the regions may be of theorder of at least about a wavelength in vacuum. A difference in losstangent may be considered significant, for example, if the difference isof about 10%. One example of a homogeneous load is a body of water. Itis noted that if different portions of the body of water is at differenttemperatures, for examples, because of non-uniform heating, thedielectric constant of the different portions may differ. If thisdifference is larger than 10%, however, the body of water may beconsidered as inhomogeneous.

A suspension of oil in water (or of any other two materials) may beconsidered homogeneous, provided that the oil droplets (or particles ofother suspended medium) are smaller than the wavelength of the appliedMSE, in vacuum. This may be so despite of the large difference indielectric constant between oil and water.

Another case in which the mode calculation or simulation may be simple,is in case of a separable load. A separable load is a load comprising atleast one entire layer of a homogeneous material. The concepts ofhomogeneity and substantially filling may be understood as explainedabove. Each layer may be bordered by cavity walls and two parallelcross-sections in a separable cavity. A separable cavity is a cavitywhere the electrical field excited therein, E(x, y, z) may be expressedas a product of the field in x, y plane by the field in the z direction,i.e. E(x, y, z)=E(x, y)*E(z). Separable cavities include, for example,cavities having a shape of rectangular box, cylinder, prism with aright-angled triangular base, or a sectioned cylinder. An example of aseparable load may be, for example, a layered cake, wherein each layeris homogeneous, and touches the cavity wall at the circumference of thecake.

In addition to recording the field patterns corresponding to the MSEsthat cause those patterns, the processor may be further configured torecord the field distribution of each field pattern corresponding tospatial locations in the energy application zone. The field pattern maybe visualized using imaging techniques or stored in a computer asdigital data. These records may be useful as input as a basis for lossprofile determination by the processor. Loss profile determination maybe sometimes facilitated by discretization, as discussed below.

An energy application zone may be discretized, such that a uniqueaddress is associated with each discretized subregion, enabling fieldpatterns to be spatially mapped to particular addresses. FIGS. 8A-8C and9 illustrate examples of discretized energy application zones. The termdiscretization may, for example, also be referred to as division,separation, or partition.

The discretization of an energy application zone into subregions may bepredetermined. In one case, a processor may acquire the predetermineddiscretization information, through, for example, a look up table,information stored in memory, or information encoded in the processor.Alternatively, discretization may occur dynamically using at least oneprocessor 30, for example as illustrated in FIG. 1. For example, whenknown dimensions of the zone are provided to the processor, theprocessor may overlay a regular or irregular division pattern on thevolume, divide the zone into subregions, and assign an address to eachsubregion.

The discretization strategy may depend on many factors, including butnot limited to: desired resolution, properties of the loss profile, andavailable field patterns. The regions may be of a regular or irregularshape. For example, in 3D cases, the regions may be regular cubic- orrectangular-shaped, as illustrated in FIG. 8A. In this case, if the size(e.g., volume) of the zone is SL, and a desired resolution may requirethe object to include at least 100 regions, then the average size ofeach region may be, for example, SL/100. Alternatively, the regions maybe any irregular-shape depending on particular needs. For example, theenergy application zone may be divided into somewhat random regions asshown in FIG. 8B. In some embodiments, the division may occur by takinginto account the location of an object in the zone and/or thecharacteristics of a specific field pattern applied to the zone.

In certain locations of the object or the energy application zone, thesize of the divided regions may be smaller than other locations. Inother words, the density of regions may vary across the entire object orenergy application zone. For example, the dividing strategy may varydepending on whether a region corresponds to a portion of an object inthe energy application zone that is targeted for energy application;whether the region corresponds to a region of the zone where no portionof the object is located, or to a region comprising a portion of theobject that is not targeted for energy application (each of the twolatter regions can be termed “void zone”). In some circumstances, thetargeted portion of the object may include the entire object. In somecircumstances, a non-occupied portion of the zone may be treated as partof the void zone. According to an exemplary strategy, the entire voidzone may be treated as a single region. In another exemplary strategy,the void zone may be divided into a plurality of regions in a similarmanner as the targeted portion inside the object. In this case, thedividing may be carried out in the entire energy application zone,regardless of the spatial occupation of the object or the spatiallocation of the targeted portion of the object. Alternatively, thedividing may be carried out separately for the zone occupied by thetargeted portion of the object and the void zone. In yet anotherexample, the void zone may be divided into a plurality of regions in adifferent manner than that in the targeted portion of the object. Forexample, the average size of regions in the void zone may be larger thanthat inside the targeted portion of the object, as illustrated in FIG.8C. In other words, the density of regions in the void zone may be lowerthan that inside the targeted portion of the object (e.g., object 50).The illustrations of FIGS. 8A-C are exemplary only. An infinite numberof discretization strategies are contemplated within the scope of theinvention.

Discretization may occur just within an area occupied by an object, oran entire energy application zone may be discretized. An example of adiscretized energy application zone 810 is discussed below in connectionwith FIG. 9. In FIG. 9, an energy application zone 810 may be dividedinto multiple regions with each region have substantially the sameregular squared shape. However, it is contemplated that the methoddescribed below may be applied to discretizations where zone 810 isdivided into regions of irregular shapes and/or unequal sizes. Theregions may be labeled from the upper left corner to lower right corneras 1, 2, 3, . . . , N_(d). An object 830 may include more than oneregions, e.g., regions R_(a) and R_(b). In this example, it may beassumed that a set of selected MSEs may be represented by [θ1, θ₂, . . .θN_(m)]. As discussed earlier, each MSE may correspond to a known fieldpattern inside the energy application zone (e.g., zone 810). Since theenergy application zone has been discretized into Nd regions, for eachMSE θ_(j), a corresponding known field pattern may be represented by aseries of local electrical field intensities [I_(1,j), I_(2,j), I_(3,j),. . . , I_(Nd,j)]. The electrical field intensity at a particular regionof the zone is proportional to the square of the electrical fieldamplitude at that region. For all applied MSEs, the field patterns maybe collectively written in matrix form as:

[I₁₁, I₂₁, I₃₁, . . . , I_(Nd1);

I₁₂, I₂₂, I₃₂, . . . , I_(Nd2);

. . .

I_(1Nm), I_(2Nm), I_(3Nm), . . . , I_(NdNm)]

This matrix, referred to as the I matrix, may be determined after theMSEs and the discretization are determined.

In some embodiments, a resolution of the different regions (for example,to which different amounts of energy are applied) and/or a resolution ofa discretization of the zone (e.g., by dividing the zone into aplurality of regions) may be a fraction of the wavelength of the appliedEM energy, e.g., on the order of λ/10, λ/5, λ/2. For example, for 900MHz, the corresponding wavelength (λ) in air (∈=1) is 33.3 cm and theresolution may be on the order of 3 cm, e.g., (3 cm)³ or 1(mm)³resolution. In water, for example, the wavelength is approximately ninetimes shorter at the same frequency (900 MHz), thus the resolution maybe in the order of 0.33 cm, e.g., (0.33 cm)³. In meat, for example, thewavelength corresponding to frequency of 900 MHz is about seven timesshorter than in air and the resolution may be in the order of 0.4 cm,e.g., (0.4 cm)³. Using higher frequencies may allow for higherresolution. For example, in other frequencies, the resolution may be inthe order of: 0.1 cm, 0.05 cm, 0.01 cm, 5 mm, 1 mm, 0.5 mm, 0.1 mm, 0.05mm or less.

For each of the plurality of field patterns, a processor may beconfigured to determine an amount of power dissipated in the energyapplication zone. An amount of power dissipated in the energyapplication zone may be the amount of power that is absorbed by anyenergy absorption medium in the zone and may be measured directly orindirectly. As an example of direct measurement, a temperature sensormay be placed at various locations in the zone, and the amount of powermay be estimated based on the temperature rise. As an example ofindirect measurement, the amount of power dissipated in the energyapplication zone may be measured by taking into account the incidentpower from the radiating element (e.g., radiating element 18), anddetermining the power reflected back and/or transmitted into at leastone of the radiating elements. The reflected/transmitted power may bereceived by radiating elements 18 functioning as receivers, and detectedby detectors 40 (see, e.g., FIGS. 1, 5A, 5B, 6, 7A and 7B). The amountof power dissipated may then determined as the difference between theincident power and the reflected (and optionally transmitted) power.

The determined amount of power dissipated in the energy application zonemay be a total power dissipated in the energy application zone. Forexample, the amount of power may include the total power that isabsorbed by the object in the zone, the walls of the zone, and/or anyother energy absorption medium in the zone. The amount of power may bedetermined, for example, as PD1-PRf, where PD1 is the total powerapplied into the energy application zone (incident power), and PRf isthe total power reflected from the energy application zone and/ortransmitted into non-emitting radiating elements.

In some embodiments, the processor may be configured to determine anamount of power dissipated only in a predetermined portion of the energyapplication zone. For example, the processor may apply selected fieldpatterns that have high field intensity areas (hot spots) covering onlya predetermined portion of the energy application zone. In that case,the determined power dissipated in the energy application zone may besubstantially dissipated in the predetermined portion, as other portionsof the energy application zone are covered by lower field intensityareas (cold spots) and may absorb a minimal amount of power.

The predetermined portion may include one or more parts of the object inthe energy application zone. In some embodiments, if the location of theobject is known, the processor may be configured to select fieldpatterns that have high field intensity areas aligned with the locationof the object or a portion of the object where energy application isdesired. Accordingly, the determined amount of power may besubstantially dissipated in desired areas of the object.

In some embodiments, the processor may be configured to differentiatebetween power dissipated in the object and power dissipated elsewhere,and associate that information with each of the plurality of fieldpatterns. In some instances, the processor may determine the total powerdissipated in the zone first, as described earlier, and then separatethe determined amount into an amount of power dissipated in the objectand an amount of power dissipated elsewhere.

The processor may differentiate using loss values associated with theenergy application zone structure (e.g., cavity walls). In someembodiments, the processor may calculate the amount of power dissipatedin the walls of the zone based on the intensity distribution of thefield pattern and the loss values associated with the walls. Thecalculation may be based on the Born approximation. In some otherembodiments, the processor may also differentiate by measuring theamount of power dissipated elsewhere. Again, this approach may alsoinvolve the use of Born approximation.

In some embodiments, the determined amounts of power for the entireapplied field pattern may be stored as a vector. For example, assumingthe set of applied MSEs may be represented by [θ₁, θ₂, . . . θ_(Nm)],and the amount of power dissipated for each applied MSE (θ_(j)) may berepresented as P_(j), then the amounts of power dissipated for the setof MSEs may form a vector [P₁, P₂, . . . P_(Nm)]. Consistent with someembodiments, the vector of dissipated power may be predetermined andprogrammed into the memory of the at least one processor before energyapplication. A vector of dissipated power may be predetermined, forexample, when similar objects are heated in an oven once and again (forexample, pizzas of similar size, shape, and composition). In someembodiments, when the vector of dissipated power is predetermined, aloss profile may be calculated based on the predetermined vector, andprogrammed into the memory of the at least one processor before energyapplication. Alternatively, the vector of dissipated power may bedetermined and stored dynamically during energy application. In someembodiments, a vector of dissipated power may be preprogrammed asdefault values, and the vector may be dynamically updated, e.g., uponuser request, during energy application.

In some embodiments, the processor may be configured to determine aspatial distribution of energy absorption characteristic across at leasta portion of the object based on the amounts of power dissipated whenthe plurality of field patterns are applied to the energy applicationzone. For example, the at least one processor may be configured todetermine the distribution of energy absorption characteristic bycalculating a distribution of indicators of absorbable electromagneticenergy in the object. An object's ability to absorb energy across itsvolume may be expressed as a “loss profile.” The term “loss” may includeany electromagnetic energy that is not reflected back to the radiatingelement that emitted it or not transmitted to another radiating element.The term “loss” may also refer to dielectric loss, which may refer tothe electric energy that is converted into heat in the object. The termprofile, which also may be referred to as a pattern, image,distribution, etc., may include any spatial distribution, for example,of loss in the energy application zone, as is discussed later in greaterdetail.

The indicators of absorbable electromagnetic energy may also be referredto as absorption coefficients, loss values, or energy absorptioncharacteristics, and may include any value indicative of energyabsorbable in the object (e.g., any value indicative of the dielectricreaction of the medium in the energy application zone to the appliedelectromagnetic energy). Examples of absorption coefficients include:electromagnetic loss due to ionic conduction (which may be referred toas ∈_(σ)″); electromagnetic loss due to dipole rotation (which may bereferred to as ∈_(d)″); and/or a combination of these or other losscomponents. In some embodiments, the absorption coefficient may be thetotal loss ∈″ which may be characterized, for example, by:

∈″=∈_(d)″+∈_(σ)″=∈_(d)″+σ′/(ω∈₀)

where ∈₀ is the electric conductivity, ω is the angular frequency of theapplied EM wave, and ∈₀ is the permittivity of free space or vacuum.Hereinafter, the total loss ∈″ (also referred to herein as a “lossparameter”) may be denoted by “σ”. However, as used herein the term“loss” is broadly used to encompass all kinds of absorptioncoefficients. By way of example, if an electromagnetic energy-absorbingobject is located in the energy application zone, the loss maycorrespond to the electromagnetic energy absorbing ability of theobject.

In some embodiments, the absorption coefficient may be a “loss tangent”,which may be defined as the ratio between the lossy and the losslessreactions to the electric field:

tan(δ)=∈″/∈′=[∈_(d)″+σ′/(ω∈₀)]/∈′

where ∈′ is the permittivity. For dielectrics with small loss tan(δ)<<1and thus, tan(δ) can be approximated by δ. This may facilitate solvingone or more equations.

As briefly mentioned earlier, losses may be characterized in term oftheir profiles (e.g., a loss profile). A loss profile may be arepresentation of any absorption coefficient as a function of locationin space. For example, a loss profile may be a map, showing areas ofdifferent tan δ (or ∈″, or any other absorption coefficient) indifferent colors. In another example, a loss profile may be a matrix,wherein each cell represents a volume cell in the energy applicationzone, and the value inside the matrix cell is a value of an absorptioncoefficient characterizing the medium in at volume cell. A loss profilemay be represented in various ways in order to convey information aboutthe distribution of energy loss in the energy application zone. A lossprofile may be represented using imaging, analytics, numerics,tablature, or any other mechanism capable of reflecting a distributionor partial distribution of energy loss. In some embodiments, a partialdistribution may refer to a loss profile that is presented only in oneor more parts (regions) of the energy application zone or the object butnot necessarily the entire zone.

When represented analytically, a loss profile may, for example, bewritten in terms of one or more equations. For example, such equationsmay be written as a function of one or more of time, space, power,phase, frequency, or any other variables that may be correlated toenergy losses, including any variables of the MS. When representednumerically, the loss profile may be expressed as a number or a seriesof numbers. Regardless of the manner of representation, a loss profilemay be expressed in either in digital and/or analog formats. Forexample, the loss profile may be a digital file stored in a memory andloadable into a processor.

The at least one processor may be configured to calculate thedistribution of energy absorption characteristics based on, anelectromagnetic field intensity associated with each of the plurality offield patterns, and power dissipated in the energy application zone ateach of the plurality of field patterns. The presentation of thedistribution of energy absorption characteristics may depend on thediscretization employed on the energy application zone

Just as the energy application zone may be discretized, in a similarmanner the loss profile may be discretized and mapped to subregions ofthe discretized energy application zone. For example, in FIG. 9, whereenergy application zone 810 is divided into multiple regions labeled 1,2, 3, . . . , N_(d), object 830 may include two kinds of materials inregion Ra and Rb, having differing loss parameters σ_(a) and σ_(b). Thevoid region (e.g., region R_(c)), which is outside the object but insideenergy application zone 810, may have a loss parameter σ_(c). In someembodiments, a loss profile 820 may be created by the processor. Lossprofile 820 may list loss values characterizing different regions inenergy application zone 810. For example, regions R_(a), and R_(b) arecharacterized by absorption coefficients σ′_(a) and σ′_(b),respectively, which approximates the real loss profile characterized byσ_(a), and σ_(b). To create this loss profile, the processor may assigneach region (1 to N_(d)) an unknown loss parameter σ_(i) (i=1, 2, 3, . .. , N_(d)). Such discretized loss profile 820 may be a numericalrepresentation of the real loss profile with a resolution characterizedby N_(d). For example, if N_(d) is larger than some given value, theremay be a correspondingly large number of regions inside the energyapplication zone and the size of each region may be smaller than ifN_(d) is equal to the aforementioned given value.

For each MSE (θ_(j)) the power loss P_(j) (which may be defined as theenergy loss per time unit) may be related to the local field patternintensities I_(ij) as follows: ½(σ₁I_(1j)+σ₂I_(2j)+ . . .+σ_(Nd)I_(Ndj))=P_(j). Accordingly, in some embodiments, the at leastone processor may be configured to construct the following equation:

½σI=P

for all MSEs, where P is a vector of the amounts of power dissipated, Iis a matrix of field pattern intensities, and σ is the loss profile,expressed as a vector of the unknown loss values.

Consistent with some embodiments, the at least one processor may befurther configured to solve the unknown loss profile such that σ may besolved mathematically. For example, σ may be solved by inverting matrixI and multiplied by vector P as follows:

σ=2PI ⁻¹  Equation (1)

While inverting I may constitute an efficient method for solving theequation, other mathematical methods may be used consistent with theinvention. These other methods may include, for example, variousstationary iterative methods such as the Jacobi method, the Gauss-Seidelmethod and the Successive over-relaxation method, etc., and variousKrylov subspace methods, such as the conjugate gradient method (CG), thegeneralized minimal residual method (GMRES) and the bi-conjugategradient method (BiCG), etc. Alternatively, the equation may also besolved using optimization approaches, e.g., minimizing the residual|½σI−P| for example, using linear or quadratic programming. Iterativemethods and optimization methods may be particularly helpful when it isdifficult to directly invert I, or when inverting I may cause largeinaccuracies in the solution (e.g., when the equation system ismathematically ill-conditioned, ill-posed, and/or singular).

As described earlier, “loss” may also be represented by absorptioncoefficients other than σ′. In some embodiments, these absorptioncoefficients may be calculated based on σ′. For example, loss tangentmay be determined as tan(δ)=σ′/ω∈′.

In some embodiments, the at least one processor may be furtherconfigured to cause the distribution of energy absorption characteristicto be stored as a look-up table. When represented in tablature, the lossprofile may assume the form of a table containing a correlation betweenphysical space and the energy absorbed at specific locations in thatspace. For example, the look-up table may dictate a relationship betweena plurality of regions of the energy application zone and theircorresponding absorption coefficients. Exemplary look-up tables ofstored absorption coefficients σ and tan(δ) are shown in FIG. 10A andFIG. 10B. The left column of each look-up table lists the labels of theregions (e.g., volumes) in the energy application zone, according to thediscretization of the zone. The right column lists corresponding σ ortan(δ) of each region.

In some embodiments, the at least one processor may be furtherconfigured to cause the display, e.g. as an image, of a distribution ofenergy absorption characteristic in at least one portion of the energyapplication zone. By way of example only, a loss profile may bedisplayed as a 2D image as shown in the right hand side of FIG. 9. Whendisplayed as an image by using any imaging techniques, the loss profilemay assume a form of a black and white image, gray-scale image, colorimage, surface profile image, volumetric image, or any other graphicaldepiction. It should be understood that the 2D image shown in FIG. 9 isa simplified example for ease of discussion. In graphical terms, theloss profile may be represented as an image, for example, in one-, two-,three-, and/or four-dimensions, wherein the forth-dimension may refer totime (e.g., a 3D spatial loss profile over time may displayed).

In some embodiments, at least one processor may be configured todetermine a location of the object based on the distribution of energyabsorption characteristics. For example, the determined loss profile amay be mapped to the energy application zone.

In FIG. 9, loss profile 820 is mapped to energy application zone 810.Loss profile 820 may reflect the spatial distribution of loss (a) inenergy application zone 810. For example, the loss profile may reflectthe energy absorption property of object 830 located in energyapplication zone 810. Because the object regions are usually associatedwith energy absorption characteristics that are distinct from those ofthe void regions, the processor may determine the location of object 830based on loss profile 820. For example, the processor may determine thecoordinates of the object 830 relative to the energy application zone810.

In some embodiments, at least one processor may be configured todetermine a location of the object based on known locations of highfield intensity (hot spots) resulting from each of the plurality offield patterns. As described earlier, the field pattern may bedetermined or predicted based on the applied MSE through testing,simulation, or analytic calculation. The prediction may be conductedonline, for example, during energy application, or may be made inadvance, for example, before an energy application cycle begins. Thepredictions may be saved, for example, in a lookup table, allowing theprocessor to use these predictions during operation according toembodiments of the present invention. The field pattern may cause one ormore high field intensity areas in the energy application zone where thefield intensities and/or the losses are high. As used herein, the terms“high field intensity area” and “hot spot” refer to a region where theelectromagnetic field intensity is substantially higher than in thesurrounding regions. In other words, these terms refer to regions whereelectromagnetic power concentrates and therefore where the transfer ofelectromagnetic energy from electromagnetic waves to an object is moreeffective than that in surrounding areas of similar absorptioncoefficient. Similarly, a “cold spot” or area of low field intensityrefers to a region where the electromagnetic field intensity issubstantially lower than the surrounding regions. Therefore, thetransfer of electromagnetic energy is less effective in low fieldintensity areas than in areas of higher field intensity, provided theabsorption coefficients are similar.

Consistent with some embodiments, the processor may either learn, or maybe preprogrammed with the coordinates of each hotspot in each fieldpattern. This is achievable because, as discussed earlier, the MSEsresult in predictable patterns with predictable high field intensityareas. The coordinates of the hotspot may indicate the location and thesize of the hotspot.

As described earlier, the processor may be configured to receive anindication that the detector has received feedback associated withenergy absorption at a particular field pattern. The processor may befurther configured to determine that an object is located in one of thehigh field intensity areas corresponding to that particular fieldpattern. The more field patterns that are applied to the energyapplication zone, the more information the processor may obtain aboutthe location and the absorptive properties of the object in the energyapplication zone. Over a series of such measurements with differingMSEs, the processor can narrow-in on the location of the object in thespace and/or the spatial distribution of absorptive properties in theenergy application zone.

By way of an example, FIG. 3C shows a field pattern with two high fieldintensity areas 84 in energy application zone 20. The areas other thanhigh field intensity areas 84 in energy application zone 20 may bereferred to as low field intensity areas or cold spots. The fieldpattern shown in FIG. 3C may be predetermined, and as a result, thelocation of the two hot spots 84 may be known in advance. An object 82may be located in energy application zone 20 and may be capable ofabsorbing electromagnetic energy. The processor may be configured toreceive from detectors feedback information indicative of energyabsorption, such as the amount of power dissipated in energy applicationzone 20, as described earlier. If at least one hot spot coincides with alocation of the object, the amount of energy absorbed in the energyapplication zone may be substantially larger than the case in which thehot spot does not coincide with the location of the object. Therefore,the processor may determine that object 82 is coincides with at leastone of the hotspots 84 thus located in the area of at least one of thehotspots.

FIG. 3D shows a field pattern with two hot spots 86, one of whichcoincides with an area in energy application zone 20 in which object 82is located. Thus, a processor may be configured to receive feedbackinformation indicative of energy absorption associated with the fieldpattern of FIG. 3D, and determine that the location of object 82 iswithin at least one of the areas covered by the two horizontal highfield intensity areas 86. Therefore, using the location informationobtained associated with both FIG. 3C and FIG. 3D, the processor maythen determine that the object is with an area covered by theintersections of high field intensity areas 84 and 86, as shown in FIG.3D, in which the dashed lines correspond to the high field intensityareas 84 in the field pattern of FIG. 3C. By receiving feedback in asimilar manner from additional field patterns, the processor may moreprecisely hone-in on the location of object 82. By applying even morefield patterns, the processor may be able to determine the generalshape, or even the precise shape of object 82. The feedback informationmay also provide an indicator of the identity of the object,particularly if the loss profile of the object is known, and theprocessor merely has to identify the location and orientation of theobject based on the feedback information received from the energyapplication zone.

In some embodiments, the processor may be further configured to causediffering amounts of energy to be applied to differing portions of theenergy application zone based on the distribution of energy absorptioncharacteristics. For example, differing amounts of energy may bedelivered to regions R_(a) and R_(b) (illustrated in FIG. 9) withinobject 830.

In some embodiments, the differing amounts of energy may be determinedbased on the distribution of energy absorption characteristics in theenergy application zone. That is, once an object's ability to absorbenergy throughout its volume is determined then energy can be applied tothe object in a controlled manner in order to achieve a desired goal.For example, if the goal is to apply energy such that it is uniformlyabsorbed across an object's volume, then the processor may selectcombinations of MSEs that result in uniform energy absorption across theobject. For instance, a smaller amount of energy may be applied to apart of the object that is associated with a higher absorption rate anda larger amount of energy may be applied to another part of the objectthat is associated with a lower absorption rate, such that the amountsof energy absorbed by the two regions are substantially the same. If onthe other hand, non-uniform energy application is desired, then theprocessor may apply amounts of energy with each of the field patternssuch that the overall energy absorption corresponds to the desirednon-uniformity of energy absorption is achieved. For instance, a largeramount of energy may be applied to regions consisting of water, suchthat the water in the object is dried up without heating the otherconstituents in the object. More generally, a larger amount of energymay be applied to regions consisting of a particular substance, in orderto process the particular substance more intensively than othersubstances.

The processor may be configured to regulate the source in order todeliver differing predetermined amounts of energy to the energyapplication zone. For example, as previously discussed, since the mannerin which energy is distributed is a function of a number of controllablevariables and the amount of their possible settings (e.g., MSEs), theprocessor may be configured to alter MSEs in order to achieve differingenergy distributions in the energy application zone. The exemplaryapparatus as shown in FIGS. 1, 5A, 5B, 6, 7A, and 7B may be utilized toalter MSEs and apply the desired field patterns.

In some embodiments, radiating elements may be selected for exciting acertain mode in accordance with the positioning of the radiatingelements in the energy application zone. The position of the radiatingelement may be selected to effectively excite a desired mode and/or toreject an undesired mode. This and other optional features of someembodiments are explained below in reference to FIGS. 12A, 12B, 12C,13A, and 13B.

The concept of rejecting modes may be illustrated by FIGS. 12A and 12B,which show X-Y cross sections of two modes 1802 and 1806 excitable incavity 1800. Mode 1802 is a TM₁₁ mode and mode 1806 is a TM₂₁ mode. ModeTM₁₁ may be excitable at every frequency that is equal to or greaterthan a lower cutoff frequency f₁₁ and TM₂₁ may be excitable at everyfrequency that is equal to or greater than a higher cutoff frequencyf₂₁. Thus, at intermediate frequencies between f₁₁ and f₂₁, TM₁₁ may beexcited without exciting TM₂₁, but there is no frequency at which TM₂₁is excitable and TM₁₁ is not. Therefore, if one desires exciting TM₁₁ ata frequency higher than f₂₁ without exciting TM₂₁, TM₂₁ may need to berejected. In the present discussion, rejecting a mode may refer topreventing or substantially decreasing the excitation of the mode.

In some embodiments, a desired mode may be excited and an undesired modemay be simultaneously rejected by selecting for the excitation aradiating element positioned at or near a null of the undesired mode,and at or near a maximum of the desired mode. A null of a mode is anylocation in the energy application zone where the field intensity of themode is permanently (or in all phases) zero, and a maximum of a mode isany location where the field intensity of the mode reaches an overallmaximal value at all phases (or at every instant). A radiating elementpositioned at the null of a mode does not excite the mode (regardless ofthe frequency applied), and a radiating element positioned near the nullmay excite the mode only to a small degree. For example, in FIG. 12Bplane 1803 is a collection of null points of mode TM₂₁; thus, aradiating element positioned at any point along this line may not excitemode TM₂₁, even at frequencies higher than f₂₁. However, since line 1809(which is along plane 1803) is not at a null of mode TM₁₁ (1802), mode1802 may be excited by a radiating element positioned at line 1809. Inpractice, the radiating element may be positioned anywhere on plane 1803without exciting mode 1806. In some embodiments, however, the radiatingelements may be positioned at the upper (and/or lower) base of thecavity, at a position in the XY plane.

Another way to reject a mode may include using two or more radiatingelements, positioned at two or more locations where the magnitude of theelectric field of the mode to be rejected is of opposite signs. Forexample, FIG. 13A depicts the (normalized) magnitude of the electricfield of mode 1806 along line 1805. As shown in the figure, at x=0.5(which is a point on plane 1803), the field is zero, at x=0.25 the fieldis +1 and at x=0.75 the field is −1. Thus, in some embodiments, tworadiating elements, one at x=0.25 and the other at x=0.75 (or at anyother two points where the field has opposite signs and equalmagnitudes) may be selected to radiate RF waves at the same amplitudeand phase, to cancel each other, and thus reject an undesired mode. Ifthe fields at the locations of the two radiating elements have oppositesigns and different absolute values, they may still be used forrejecting the undesired mode, if, for instance, their amplitudes aretuned such that sum of the products of field and amplitude at eachradiating element location is zero. It is noted that while the abovediscussion is focused on different points along the X axis, similarconsiderations may be applied also for points having different y valuesand/or z values.

In some embodiments, a desired mode may be excited by emitting energyvia two antennas that are oriented anti parallel to each other, or thatare oriented parallel to each other but emit waves at a phase shift of180° between each other, and located at points where the field patternhas opposite sign. Similarly, in some embodiments, modes may be rejectedby emitting energy via two antennas that are oriented anti parallel toeach other, or that are oriented parallel to each other but emit wavesat a phase shift of 180° between each other, and located at points wherethe field pattern has the same sign.

FIG. 13B depicts the (normalized) magnitude of the electric field ofmode 1802 along line 1805. As shown in the figure, at x=0.5, the fieldis maximal, and the field at x=0.25 is equal (both in magnitude and insign) to the field at x=0.75. Thus, two antennas, one at x=0.25 and theother at x=0.75 that emit at the same amplitude and phase may tend toexcite mode 1802. However, two antennas that are oriented anti parallelto each other, or that are oriented parallel to each other but with aphase shift of 180° between each other, may reject mode 1802.Consequently, the latter combination of antennas and phases may excitemode TM₂₁ and rejects mode TM₁₁.

In some embodiments, a desired and/or an undesired mode is a resonantmode. A resonant mode may be excited when the frequency f of theelectromagnetic wave corresponds to the dimensions of the energyapplication zone in a manner known in the art. For example, in an energyapplication zone that is a rectangular cavity, a resonant mode may beexcited when the dimension, along which the electromagnetic wavepropagates, referred to herein as h_(z), is equal to N*(λ/2), where N isa whole number (e.g. 0, 1, 2, 3) and λ is the wavelength, given by theequation λ=c/f, where c is the light velocity in the cavity. A resonantmode is usually marked with three index numbers, where the third indexnumber is N.

When a single resonant mode is excited at a given frequency, a greatmajority of the power carried with the excitation may be carried by theresonant mode, and other modes, which may be propagating or evanescent,may carry a smaller portion of the power, which may be negligible. Thus,when a single resonant mode is excited, there may be little or no needto reject non-resonating modes. For example, when h_(z)=c/f₂₁ (i.e. whenN=2) the antennas and frequency may be selected to excite mode TM₂₁there may be little need to reject, for example, mode TM₁₁, because,although mode TM₁₁ may be excitable at the applied frequency, it maycarry only a small amount of the power, in comparison to the amount ofpower carried by the resonant mode TE₂₁₂. Thus, in some embodiments,resonant modes may be used for achieving a target field intensitydistribution. This may facilitate control over the excited modes,provided sufficient bandwidth and frequency control.

In some embodiments, mode excitation may be further facilitated, (e.g.,by easing the requirements from bandwidth and frequency control), byusing a degenerate cavity. A degenerate cavity is one in which at leastone cut off frequency is a cut off frequency of two or more modes of thesame family (e.g., two TE modes). Similarly, each resonant frequency(except for, sometimes, the lowest one) may excite two or more resonantmodes of the same family. Some shapes of degenerate cavities mayinclude, for example, cylinder and sphere.

In some embodiments, one desired resonant mode and one or more undesiredresonant modes may be excited at a same frequency, and the non-desiredmodes may be rejected as described above. For example, the samefrequency that excites mode TM₂₁₂, a cross section of which is shown as1806 in FIG. 12B may excite also mode TM₂₁₂, a cross section of which isillustrated as 1808 in FIG. 12C. However, if the excitation is via aradiating element positioned at a null of mode 1808, which is not a nullof mode 1806, only mode 1808 may be excited. For example, if theradiating element radiates at frequency f₁₂=f₂₁ at line 1809, shown inFIGS. 12B and 12C, only mode 1808 may be excited.

Thus, in accordance with some embodiments of the invention, there isprovided apparatus for determining a spatial distribution of energyabsorption characteristics across at least a portion of an energyapplication zone based on amounts of power dissipated when a pluralityof predetermined modes are applied to the energy application zone. Modesother than the predetermined ones may be rejected, for example, asdescribed above.

In some embodiments, the same field patterns used to obtain the energyabsorption characteristic profile (also referred to as spatialdistribution of energy absorption characteristic) may be used to applythe differing amount of energy to the object. For example, the apparatusof FIG. 1, 5A, 5B, 6, 7A or 7B may be utilized to apply frequencymodulated electromagnetic waves to the zone for measuring thedistribution of energy absorption characteristics as well as fordelivering the energy to the object in the zone. In some embodiments,the field patterns applied to deliver the differing amount of energy tothe object may be different from those selected to obtain the energyabsorption characteristic profile. For example, frequency modulation(e.g., as obtained with the apparatus of FIG. 5A) may be utilized formeasuring the distribution of energy absorption characteristics, andphase modulation (e.g., with the apparatus of FIG. 6) may be utilizedfor delivering the energy to the object in the zone. Additionally, anycombination may be used. For example, phase modulation (e.g., using theapparatus of FIG. 6) may be utilized for measuring the distribution ofenergy absorption characteristics, and a combination of phase andfrequency modulations may be utilized for delivering the energy to theobject in the zone.

In some embodiments, the at least one processor may be furtherconfigured to recurringly determine the distribution of energyabsorption characteristic (for example few times during an energyapplication process, e.g., a heating process). This may be desirablewhen, for example, distribution of energy absorption characteristicchanges over time, as may occur, for example, when the temperature ofthe substance rises; when phase change occurs (e.g., ice melts andbecomes water); when moisture evaporates; or when other properties of anobject changes. In these and other instances, the processor may be usedto recurringly determine the distribution of energy absorptioncharacteristics during the energy application process.

A time lapse between two recurringly determined distributions of energyabsorption characteristics may be pre-determined. By way of exampleonly, the processor may be preprogrammed to determine the distributionevery five seconds, one second, fraction of a second, or at some lesseror greater interval. Alternatively or additionally, the time lapsebetween two recurringly determined distributions of energy absorptioncharacteristics may change dynamically, based on certain characteristicsof the energy application process.

A time lapse between two recurringly determined distributions of energyabsorption characteristics may be a function of the magnitude ofdifference between two or more distributions of energy absorptioncharacteristics determined earlier. For example, the decision on thetime lapse from the second determination of a loss profile to the thirdmay depend on the difference between the results of the first and seconddetermined profiles. In some embodiments, the “difference” may be anumerical measure, e.g., the sum of differences in the absorptioncoefficients at all the regions of the zone. In some embodiments, the“difference” may be a graphical measure, e.g., the distance between twodistributions as displayed as an image. The magnitude of the differencemay suggest how dramatic the change of energy absorption characteristicsis in the zone. Accordingly, the distribution may be updated at a higherrate if the distribution changes more dramatically.

In some embodiments, the time lapse may be inversely proportional to themagnitude of the difference. For example, when the difference is 1×10⁻⁶,the time lapse may be 1 second, and when the difference is 2×10⁻⁶, thetime lapse may be 0.5 second. It is to be understood that the time lapsemay also be inversely associated with the difference using othermathematical relationships, and the foregoing are examples only.

In some embodiments, the time lapse between two recurringly determineddistributions of energy absorption characteristics may be a function ofphysical characteristics of the object. For example, the time lapse maybe larger when the object contains a substantially amount of protein andfat (e.g., meat), and smaller when the object contains mostly water orice, and vice versa.

FIG. 14 is a simplified block diagram of a processor 630 configured toconstruct a loss profile of at least a portion of an energy applicationzone, for instance, cavity 20 of FIG. 1, in accordance with someembodiments. Processor 630 may be the same as, may include, or may bepart of processor 30. Additionally or alternatively, processor 630 maybe in addition to processor 30.

Processor 630 is shown to include storage 632 (which may also bereferred to as memory) for storing data, and several processing modulesfor processing data, for example, data stored in storage 632. Storagespace 632 may be continuous, segmented, or may have any otherconfiguration as known in the art of storing data electronically. Themodules may be implemented using hardware and/or software and mayinclude, for example, software routines. In some embodiments, two ormore of the modules shown in FIG. 14 may be united to a single module,which performs the tasks of the two modules, or may be spread amongseveral modules.

Processor 630 may be connected to an interface 610, for receiving datavia the interface. For example, field patterns that may be obtained withdifferent MSEs may be received from the interface, and stored in storage632, for example, in dedicated storage space 634. Storage space 634 mayalso store the MSEs, such that each stored MSE may be associated with astored field pattern, predicted to be excited in the energy applicationzone when energy is applied to the zone at that MSE. The field patternsassociated with the MSEs may be obtained with the energy applicationzone being empty, and/or the energy application zone having a standardload in it. The standard load may be chosen to be similar to typicalloads intended to be used in the energy application zone (for exampleone or more foods that are usually cooked in an oven, or that the ovenis expected to cook often).

In some embodiments, storage 632 may also have storage space 636, forstoring a loss profile of the energy application zone or portion(s) ofthe energy application zone. For example, storage space 636 may store aloss profile of the energy application zone obtained in a preceding lossprofile reconstruction cycle. Additionally or alternatively, storagespace 636 may store a predicted loss profile. The prediction may beobtained based on knowledge of the object in the energy applicationzone, its composition, location, orientation, temperature, and/or anyother parameter that may affect the loss profile. The stored lossprofile may be sent to storage space 636, for example, from interface610, from another interface (not shown), or from an equation solvingmodule 648 described below. For example, the stored loss profile may becalculated or otherwise predicted by another apparatus and/or at anearlier date, and sent to storage space 636 via interface 610. Storage632 may also have a storing space 638 for storing energy distributionsand/or field intensity distributions obtained in the energy applicationzone during energy application.

Processor 630 may include an MSE determination module 642. This modulemay be configured (e.g., by running a suitable software) to determinewhich of the available MSEs are to be used at any stage of operation,e.g., during an energy application process. In some embodiments, all theavailable MSEs may be used by default, and the MSE determination module642 may be omitted. In other embodiments, module 642 may determine MSEsto be used, for example, based on the predicted loss profile. Module 642may retrieve predicted loss profile data stored on storage space 636.Alternatively or additionally, module 642 may select MSEs that arerelatively easier to excite and/or control, and may select other MSEsonly if, for example, the easily excited MSEs do not providesatisfactory results.

Module 642 may be connected to control module 660, which may controlsource 650 of electromagnetic energy to excite the selected MSEs. Source650 may include power supply, a modulator, an amplifier, and/orradiating element(s) or portions thereof (for example power supply 12,modulator 14, amplifier 16, and radiating element 18 illustrated in FIG.1). In some embodiments, the energy distribution obtained in the energyapplication zone as a result of the excitation may be measured. Themeasurements may be carried out by one or more detectors, showncollectively as 640. One or more of detectors 640 may be a part ofsource 650, and the others, if any, may be separate and/or independentfrom source 650. It is noted that source 650 and detector 640 may inpractice be embodied in the same parts, for example, the same antennasmay be used for supplying energy to the energy application zone and formeasuring excited field patterns, even if not necessarily at the sametime. The results of the measurements may be stored on storage space638.

Processor 630 may also include a discretization module 644, configuredto divide the energy application zone to regions, for example, asdepicted in FIG. 8A, 8B, or 8C. Discretization module 644 may divide theenergy application zone in accordance with a loss profile stored instorage space 636. For example, module 644 may divide the zone moredensely where more abrupt loss changes are present in the predicted lossprofile. In some embodiments, the predicted loss profile may be providedin accordance with a given discretization, for example, as a matrix ofvalues, each associated with one portion of the energy application zone.Module 644 may then discretize the energy application zone in accordancewith the discretization by which the predicted profile is provided.Module 644 may retrieve data from storage space 636, saving thepredicted profile. For example, module 644 may divide the energyapplication zone such that volumes characterized by similar losses willbe included in a single region. Discretization module 644 may alsodivide the energy application zone in accordance with a predetermineddiscretization scheme, for example, a default discretization scheme. Onepossible default discretization scheme is illustrated in FIG. 8A.

Processor 630 may also include an equation constructing module 646,configured to construct equations according for example, equation 2(below) to be solved in order to obtain the loss profile. Module 646 maydefine the field intensity of each of the MSEs which may be selected bymodule 642, in each region to which the energy application zone isdivided by module 644, and may take into account measurement resultsstored at storage space 638.

Once the equations are constructed by module 646, equation solvingmodule 648 may solve the equations, for example, by linear programmingor any other means known in the art for solving linear equations. Ifequation solving module 648 determines that the equations are notsolvable or that the solution is not satisfactory, for example is notsufficiently stable, module 648 may trigger module 642 and/or module 644to amend the selected MSEs and/or the discretization.

If the equations are solved, the obtained loss profile may be saved, forexample, at storage 636, for further use. One further use may be as aprediction for a future loss profile, for instance, after the objecttemperature changes. Another future use may be to guide energyapplication to the energy application zone.

The invention may include a method for applying electromagnetic energyto an object. Such an energy application may be accomplished, forexample, through at least one processor (for example processor 30 or630) implementing a series of steps such as those set forth in process1000 as set forth in the flow chart of FIG. 11. Process 1000 may be usedto dynamically determine a loss profile 820 for a given energyapplication zone, which may include an object, for example, object 830(FIG. 9).

Process 1000 may include causing a source of electromagnetic energy toapply a plurality of electromagnetic field patterns to an energyapplication zone, which may include an object. As indicated in FIG. 11,the processor may determine a set of MSEs for use in step 1010. Asdiscussed previously, an MSE may be correlated to a known field pattern.Therefore, by determining a set of MSEs, the processor may controlapplication of electromagnetic energy to the energy application zone andgenerate a set of known field patterns in the zone. In some embodiments,all available MSE may be used and step 1010 may be omitted.

The method of constructing a controlled EM field pattern inside theenergy application zone from a predetermined set of field patterns maybe referred to as “EM spatial filtering.” The term “filtering” refers toan ability to discriminate spatial locations and the field intensitiesthereof in terms of a set of known EM field patterns. And since each ofthe predetermined set of field patterns can be correlated with one ormore controllable MSEs, it is possible to represent a controlled EMfield pattern in terms of one or more MSEs. It should be understood thatthere may be more than one MSE or MSE combinations available to achievea given field pattern. The choice of MSE to achieve a particular fieldpattern may be application dependent, e.g., locations where it isdesirable to apply EM energy.

In step 1010, a set of MSEs suitable for the process may be determined.For example, a processor may control the energy source to supply EMenergy at a plurality of frequencies. In this case, the plurality offrequencies may serve as controllable MSE variables in this process.Alternatively or additionally, the processor may control the energysource to supply EM energy in a plurality of amplitudes. In this case,amplitudes may serve as controllable MSE variables in the process. Asdescribed earlier, the selected MSEs may be stored as a MSE matrix.

The processor may cause the source to apply the desired field patternsto the energy application zone (e.g., 810 in FIG. 8), by executing theselected MSEs (step 1030: apply MSEs). Consistent with some embodiments,exemplary apparatus as shown in FIGS. 1, 5A, 5B, 6, 7A and/or 7B may beused to apply the field patterns.

In step 1020, a discretization strategy may be applied to divide theenergy application zone (e.g., 810 in FIG. 9) into a plurality ofregions. In some embodiments, the process may discretize the space withthe following logic. At first, a default discretization strategy (e.g.,scheme) may be applied. For example, the energy application zone may bedivided to a predetermined number of regions with equal size and shape.The typical size of each such region may be determined in accordancewith the MSEs (e.g., frequencies) expected to be applied during energyapplication. For example, the regions may be rectangular, with each edgehaving a size of a half, quarter, or other portion of the longestwavelength expected to be applied during energy application. Thewavelength used for setting an initial region size may be the wavelengthin air, for example, in cases where light velocity in the energyapplication zone is not known. Feedback obtained from the energyapplication zone may then be used to determine absorption coefficientscharacteristics of each of the regions. Then, the regions identified toabsorb energy better than others may be discretized to smaller regionsto improve the resolution. Regions that show very low energy absorbancemay be coalesced. This process may continue until a required resolutionis obtained, until the smallest region is of a certain predeterminedsize, or when any other stopping criterion is met.

In some embodiments, other discretization strategies may be used. Forexample, some initial information regarding the position and orientationof the object may be obtained, for example, from a user and/or from acamera imaging the energy application zone, for example, with visiblelight, and then, discretization occurs such that areas occupied with theobject are discretized to smaller regions than other areas. In someembodiments, when loss profile determination is recurring, the lossprofile obtained in a preceding determination may be used as input fordetermining the discretization in a following loss profiledetermination.

The foregoing are but some discretization strategies and the inventionis not limited to any particular discretization strategy. Rather, adiscretization strategy in accordance with presently disclosedembodiments may include any suitable method for causing the processor torepresent the energy application zone or the object in it as multipleregions. FIG. 9 is but one example of discretized energy applicationzone 810, where object 830 occupies multiple regions.

Given a discretization, position of the object and/or loss profile ofthe energy application zone may be determined as follows.

First, the processor may either learn, or may be preprogrammed with thecoordinates of each hot spot in each field pattern corresponding to eachMSE. This is achievable because, as discussed earlier, the MSEs resultin predictable patterns with predictable hot spots. Therefore, when theprocessor receives an indication that the detector has received feedbackindicative of absorption during a particular MSE condition, theprocessor may determine that an object portion may coincide with one ofthe hotspots corresponding to that MSE condition. The more MSEs that aretested for feedback, the more information the processor learns about thelocation and the absorptive properties of the object in the energyapplication zone. Over a series of such measurements with differingMSEs, the processor may narrow-in on the location of the object in thespace and/or the absorptive properties in each discrete region.

In step 1030, the processor is configured to apply MSEs and controls theEM energy to be supplied into the energy application zone. For eachapplied MSE, the energy loss in the energy application zone may bemeasured. For example, such energy loss may be measured by comparing theamount of incident energy applied to the energy application zone to theamount of energy detected to leave the energy application zone, whichmay include reflected energy, detected by the same radiating elementthat emitted the incident energy, and transmitted energy, detected byother detectors. The difference between the incident energy and the sumof reflected and/or transmitted energies may correspond to the energyloss in the energy application zone.

In some embodiments, the energy loss can be represented by applicationduration and power loss P. The power loss may be determined from theincident, reflected, and transmitted powers Since for each MSE (θj) thepower loss Pj may be related to the local intensities Iij as follows:

½(σ₁ I _(1j)+σ₂ I _(2j)+ . . . +σ_(Nd) I _(Ndj))=Pj,

the measured power loss P, the matrix I and the unknown loss profile σmay satisfy the following equation constructed from the measured powerloss P and known intensities Iij:

½σI=P.  Equation (2)

In step 1040, the processor is configured to construct the equation, forexample the processor may construct the equation for solving the unknownloss profile σ in accordance with equation 2. While the unknown lossprofile σ may be solved mathematically from the above equation, theequation is not guaranteed solvable, e.g., the I matrix may be singular.In some other cases, while the equation is solvable, the solution may beinaccurate because, for example, the I matrix may be mathematicallyill-conditioned and/or ill-posed. Therefore, in step 1050, a check maybe performed to determine if the equation is solvable at a desiredaccuracy (referred to herein as “solvable”). For example, a processormay calculate the determinant of the I matrix and determine if it issingular. As another example, a processor may calculate the conditionnumber of the I matrix to determine if it is ill-conditioned.

If the above equation is solvable (step 1050: yes), in step 1070, theloss profile σ may be solved from the equation using methods such asdirect inversion, or various iterative methods, as discussed earlier. Ifthe equation is not solvable (step 1050: no), step 1060 may be conductedwhere the MSEs and/or the discretization strategy is modified andprocess 1000 goes back to step 1030. For example, a new set of MSEs maybe chosen and applied to the zone, and power dissipated in the zone maybe measured accordingly for each new MSEs.

The above-described process may also be a base for energy applicationprocess, where the energy is applied in accordance with the obtainedloss profile. Such energy application process may include, for instance,optional steps 1080 and 1090.

In step 1080, electromagnetic energy may be applied to the energyapplication zone based on the loss profile. In some embodiments, aplurality of differing amounts of electromagnetic energy may beselectively applied to differing regions of the energy application zone.For example, a processor may first select a plurality of MSEs to beapplied, and each of the plurality of MSEs may generate a differentfield pattern in the energy application zone. Then the processor maydetermine the amount of power to be used for applying each MSE and/orthe amount of time for supplying the power for each MSE, based on thedesired amount of electromagnetic energy to be applied to each regionand the loss profile created in step 1070.

In step 1090, a determination may be made as to whether a new lossprofile is needed. In some embodiments, a new loss profile may be neededat predetermined time intervals, such as, every five seconds or otherinterval. In some other embodiments, the determination may be based onthe magnitude of a difference between two recurringly determined lossprofiles. In yet some other embodiments, the determination may be basedon characteristics of the object, such as size, position, shape of theobject, and/or substances contained in the object. In some embodiments,the determination may be based on the quality of the loss profile, forinstance, if the loss profile is not of sufficient resolution, process1000 may be repeated, optionally starting at step 1010, where MSEs aredetermined based on the low resolution loss profile already at hand. Insome embodiments, if a new loss profile is needed (step 1090: yes),process 1000 may go back to step 1030 for determining a new lossprofile. If a new loss profile is not needed (step 1090: no), process1000 may be terminated.

In some exemplary embodiments, the processor may regulate the source toapply energy repetitively to the energy application zone. For example,the processor may apply an MSE and cause its corresponding field patternin the energy application zone for a predetermined time period, thenapply another MSE and cause another field pattern in the energyapplication zone for another predetermined time period. Such energyapplication duration and/or energy application rate may vary. Forexample, in some embodiments, energy may be applied to the energyapplication zone 120 times per second. Higher (e.g. 200/second,300/second) or lower (e.g., 100/second, 20/second, 2/second, 1/second,30/minute) rates may be used, as well as uneven energy applicationrates.

In some embodiments, a set of MSEs may be applied sequentially during aperiod of time (herein referred to as “MSE scanning”). As used herein,“MSE scanning” is interchangeable with “MSE sweeping.” Both “scanning”and “sweeping” may include changing MSEs in one dimension ormulti-dimensions. For example, a one-dimensional scanning may refer tochanging MSE by changing only frequency, phase, or amplitude. Amulti-dimensional scanning may refer to changing MSE by changing two ormore of frequency, phase, and amplitude, or any other variables that maybe included in an MSE. An MSE scanning may also be repeated at apredetermined rate or after a predetermined interval. At times, asequence of one or more scans may be performed, e.g., once every 0.5seconds or once every 5 seconds or at any another rate. The MSEselection in different scans may or may not the same.

After a given amount of energy (e.g., a predetermined number of Joulesor kilo-Joules, for instance, 10 kJ or less or 1 kJ or less or severalhundreds of joules or even 100 J or less) has been transmitted ordissipated into the load or into a given portion of a load (e.g., byweight such as 100 g or by percentage, such as 50% of load), a new scanmay be performed.

In some exemplary embodiments of the invention, the rate of energyapplication or the rate of scan (for example, the duration of energyapplication at each MSE within a scan, the total duration of each scan,energy application interventions between scans, etc) may depend on therate at which feedback from the energy application zone changes betweenscans. For example, energy application may start with a trial scan rate,and if differences in feedback between successive scans are above apredetermined upper threshold, the scan rate may be increased. If thechange is below a lower threshold (which may be the same as or lowerthan the upper threshold) the scan rate may be lowered. For example, athreshold of change in dissipation (e.g., a 10% change in sum integral)may be provided or different change rates associated with differentenergy application/scan rates, for example using a table. In anotherexample, what is determined is the rate of change between energyapplications/scans (e.g., if the average change between energyapplications/scans is less than the change between the last two energyapplications/scans). Such changes may be used to adjust the periodbetween energy applications/scans once or more than once during energyapplication process. Optionally or alternatively, changes in the system(e.g., movement of the object or structure for hold the object) mayaffect the energy applications/scans rate (typically major changesincrease the rate and minor or no changes decrease it).

In the foregoing Description of Exemplary Embodiments, various featuresare grouped together in a single embodiment for purposes of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed invention requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the followingclaims are hereby incorporated into this Description of the ExemplaryEmbodiments, with each claim standing on its own as a separateembodiment of the invention.

Moreover, it will be apparent to those skilled in the art fromconsideration of the specification and practice of the presentdisclosure that various modifications and variations can be made to thedisclosed systems and methods without departing from the scope of theinvention, as claimed. Thus, it is intended that the specification andexamples be considered as exemplary only, with a true scope of thepresent disclosure being indicated by the following claims and theirequivalents.

1.-39. (canceled)
 40. An apparatus for applying radio frequency (RP)energy to an object in an energy application zone via at least oneradiating element, the apparatus comprising: at least one processorconfigured to: cause RF energy to be applied at a plurality ofelectromagnetic field patterns to the object in the energy applicationzone; for each of the plurality of field patterns, determine an amountof power dissipated in the energy application zone; and determine aspatial distribution of energy absorption characteristics across atleast a portion of the energy application zone based on the amounts ofpower dissipated when the plurality of field patterns are applied to theenergy application zone.
 41. The apparatus of claim 40, wherein theprocessor is further configured to determine a spatial distribution ofenergy absorption characteristics across at least a portion of theobject.
 42. The apparatus according to claim 40, wherein the at leastone processor is configured to calculate the spatial distribution ofenergy absorption characteristics based on an electromagnetic fieldintensity associated with each of the plurality of field patterns andpower dissipated in the energy application zone at each of the pluralityof field patterns.
 43. The apparatus according to claim 40, wherein theat least one processor is configured to determine a location of theobject based on the spatial distribution of energy absorptioncharacteristics.
 44. The apparatus according to claim 40, wherein the atleast one processor is configured to determine a location of the objectbased on known locations of high field intensity areas resulting fromexciting each of the plurality of field patterns.
 45. The apparatusaccording to claim 40, wherein the at least one processor is configuredto recurrently determine the spatial distribution of energy absorptioncharacteristics.
 46. The apparatus according to claim 40, wherein the atleast one processor is further configured to cause differing amounts ofenergy to be applied to differing portions of the energy applicationzone based on the spatial distribution of energy absorptioncharacteristics.
 47. The apparatus according to claim 40, wherein the atleast one processor is further configured to cause differing amounts ofenergy to be applied to differing portions of the energy applicationzone, such that similar amounts of energy are applied to regions ofsimilar energy absorption characteristics and different amounts ofenergy are applied to regions of different energy absorptioncharacteristics.
 48. The apparatus according to claim 40, wherein the atleast one processor is further configured to cause differing amounts ofenergy to be applied to differing portions of the energy applicationzone, such that similar amounts of energy are absorbed by regions ofdiffering energy absorption characteristics.
 49. The apparatus accordingto claim 40, wherein the at least one processor is further configured tocause differing amounts of energy to be applied to differing portions ofthe energy application zone, such that a predetermined spatialdistribution of energy absorption is obtained in the energy applicationzone.
 50. The apparatus according to claim 40, wherein the at least oneprocessor is further configured to cause controlled amounts of energy tobe absorbed at differing regions in the object.
 51. The apparatusaccording to claim 40, wherein the at least one processor is configuredto determine an amount of power dissipated only in a predeterminedportion of the energy application zone.
 52. The apparatus according toclaim 51, wherein the predetermined portion includes one or more partsof the object in the energy application zone.
 53. The apparatusaccording to claim 40, further comprising a source of electromagneticenergy, wherein the source includes at least one of a phase modulator,frequency modulator and amplitude modulator.
 54. The apparatus accordingto claim 40, further including at least one radiating element configuredto apply RF energy to the energy application zone.
 55. The apparatusaccording to claim 40, further comprising a source of electromagneticenergy, wherein the source includes at least one radiating elementconfigured to apply RF energy to the energy application zone.
 56. Theapparatus according to claim 40, wherein the energy application zone isa resonant cavity.
 57. The apparatus according to claim 40, wherein theenergy application zone is a modal cavity.
 58. The apparatus accordingclaim 40, wherein the processor is further configured to regulate thesource to repetitively apply energy to the energy application zone at aninterval of between 0.5 seconds and 5 seconds.
 59. An apparatus forapplying radio frequency (RF) energy to an object, the apparatuscomprising: a source of electromagnetic energy; an energy applicationzone; and at least one processor configured to: cause RF energy to beapplied in a plurality of electromagnetic field patterns to the objectin the energy application zone; for each of the plurality of fieldpatterns, determine an amount of power dissipated in the energyapplication zone; and determine a spatial distribution of energyabsorption characteristics across at least a portion of the object basedon the amounts of power dissipated when the plurality of field patternsare applied to the energy application zone.
 60. An apparatus forapplying electromagnetic energy in the radio frequency range (RF energy)to an energy application zone via at least one radiating element, theapparatus comprising: at least one processor configured to: controldistribution of RF energy such that at least two mutually differentelectromagnetic field patterns are applied to the energy applicationzone; for each of the electromagnetic field patterns, determine anamount of power dissipated in the energy application zone; and determinea spatial distribution of energy absorption characteristics across atleast a portion of the energy application zone based on the amounts ofpower determined for each of the field patterns.